# Problem of Missing Data

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 VASA Mission of VA Statisticians Association (VASA) Promote & disseminate statistical methodological research relevant to VA studies; Facilitate communication & collaboration among VA-affiliated statisticians; Promote good statistical practice; Increase participation & visibility of VA statisticians at national meetings such as the VA HSR&D and ASA Joint Statistical Meetings; Increase participation of statisticians in VA research merit review 1 / 46

2 Poll Your affiliation and title: Your Research areas: Your level of statistical knowledge: beginner, intermediate, and advanced Topic of future statistical cyberseminar you like to take: Need of statistical help in your research: No, Yes. 2 / 46

3 Problem of Missing Data Standard statistical methods have been developed to analyze rectangular data sets. The rows are observation units The columns are variables. The entries are values (real numbers). The concern is what happen when some of these values are not observed. Most statistical software creates special codes for the missing values Some statistical software exclude subjects with missing values - complete-case analysis, which will be valid in a very limited cases. 3 / 46

4 Missing-data Pattern and Mechanism Which method to choose for the analysis of missing data depends on missing-data patterns, as well as the missing-data mechanism. 4 / 46

5 Univariate Missing Data Pattern A B C NA NA NA This data set has three variables A, B and C, and the variable C has missing values, denoted by NA. It can be seen that five of the eight subjects in the data set are completely observed, while the values of variable C of the other three subjects are missing. This is the simplest missing data pattern. 5 / 46

6 Attrition in Longitudinal Studies Attrition (dropout) in longitudinal studies is a very frequent occurrence, especially for long follow-ups or difficult study populations such as children. If in a study, subjects drop out before the end of the study and do not return, then this scenario leads to the so called monotone missing data pattern. 6 / 46

7 Example on Attrition A multi-clinic observational study on a prospective cohort of primary care patients with clinical depression. The study evaluated depressive symptoms, mental and physical health for 966 clinically depressed persons from 6 large U.S. clinics. These persons responded to several questionnaires that measured their physical and mental health at baseline, 6 weeks, 3 months, and nine months after baseline. At 9 month after baseline each patient was interviewed by a psychiatrist who determined whether the patient still suffered from clinical depression after nine months. 7 / 46

8 Example on Attrition, continued Unit non-response over time (X: observed, M=missing) Baseline 6 weeks 3 months nine months Freq X X X X 759 X X X M 92 X X M M 27 X M M M 2 8 / 46

9 File-matching Missing Data Pattern Sometimes two or more variables are collected on units, but are never jointly observed. A B C NA 99 6 NA NA NA NA 32 NA 5 48 NA NA 25 NA NA / 46

10 File-matching Missing Data Pattern, Continued It is important to know that for this missing data pattern, parameters relating to the association between these jointly unobservable variables (A,B,C) are not estimable from the data. In the above data, there is no information in the data about the partial associations of B and C given A. In practice, analyses of data with this pattern require to make strong assumptions about these partial associations. 10 / 46

11 General Missing Data Pattern) A B C D NA NA 28 NA NA NA 41 NA NA NA NA NA / 46

12 Missing Data Mechanism Understanding the missing data mechanism is important for the analysis of the missing data. Rational of using a method for dealing with a missing data set relies on the missingness mechanism. To explain the missing data mechanisms, we first define a vector of indicator variables R that identify which variables are observed and which are missing. For example, R = (0,1) T indicates that the first variable is missing and the second variable is observed. 12 / 46

13 Assumption on Missing Data Assumption: Missingness indicators hide true values that are meaningful for analysis. 13 / 46

14 Example on Death Consider a randomized trial with two treatments, and suppose that a primary outcome of the study is a quality-of-life health score Y measured one year after randomization to treatment. For participants who die within a year of randomization to treatment, Y is not available due to death. 14 / 46

15 Poll Do you consider patients who died before the end of the study as missing quality-of-life health score? Yes No Not Sure 15 / 46

16 Example on Death, Continued Do you consider patients who died before the end of the study as missing quality-of-life health score? It does not make sense to treat those outcomes as missing, given that quality of life is meaningless concept for people who not alive. 16 / 46

17 Example on Non-response in Opinion Polls We are interested in polling individuals about how they will vote in a future referendum, where the available responses are yes, no, or missing. 17 / 46

18 Poll Do you consider patients who with missing as missing response? Yes No Not Sure 18 / 46

19 Example, Continued Individuals who fail to respond to the question may be refusing to reveal real answers or may have no interest in voting. Assumption would not apply to individuals who would not vote, and these individuals define a stratum of the population that is not relevant to the outcome of the referendum. Assumption would apply to individuals who do not respond to the initial poll but would vote in the referendum. For these individuals it would make sense to treat their responses on the referendum as missing. 19 / 46

20 Missing Data Mechanism Since some of the variables Y in the data set may be missing, we partition Y into two parts, Y obs and Y mis, the observed part and the missing part. Below we introduce the three missing data mechanisms, missing completely at random (MCAR), missing at random (MAR) and missing not at random (MNAR). 20 / 46

21 Missing Completely at Random (MCAR) The data are called MCAR if missingness does not depend on the value of data Y, missing or observed. Statistically, that is f (R Y ) = f (R) for all Y. (1) The consequence of the above relationship means that missingness indicator is conditionally independent of the study variables, so data on the study variables, regardless of missing or observed, have nothing to do with the mechanism that the data are missing. 21 / 46

22 Example on MCAR Consider an experiment involving random sampling. Under MCAR people with missing values are really just a random sample of the study population. As a result, people with observed data still make up a valid random sample from the study population for the ultimate inference, though with some loss in efficiency because of the smaller sample size. Therefore when data are MCAR, you can ignore the units with missing values and proceed with the complete data analysis, and still make valid inference. 22 / 46

23 Missing at Random (MAR) MAR is a less restrictive assumption on missing data mechanism than MCAR. Data are called MAR when missingness depends only on the observed components Y obs of Y, but not on the missing components Y mis. Statistically, that is f (R Y ) = f (R Y obs ) for all Y mis. (2) Despite its name, MAR does not mean that the missing data are a simple random sample of all data values, which is the case for MCAR. MAR lessens MCAR in that the missing values can behave like a random sample of all values within subpopulations defined by the observed data rather than the entire data values. 23 / 46

24 Example on MAR In many VA studies, race is a the key variable but missing substantially. If the reason for missing race is only related to age of a veteran, and if age is observed for all study subjects, the MAR holds. 24 / 46

25 Missing not at random (MNAR) The mechanism is called missing not at random (MNAR) if the distribution of R depends on the missing values in Y. Strictly speaking, MNAR comes in two forms: (i) missingness depends on the missing value itself or (ii) missingness depends on an unobserved variable. The latter is common in latent variable models or hidden Markov models. 25 / 46

26 Example on MNAR If the reason for missing race is related to race itself or some unmeasured covariates, the MAR does not hold. 26 / 46

27 Illustration Example We demonstrate the three mechanisms and their consequences through the following simple example. Consider a simple linear relationship between two variables x and y, where the predictor variable x is fully observed, but some of y are missing according to different missing mechanisms. The variables x and y follow the linear regression y = x + ε, where x and ε independently follows standard normal distributions. We generate an independent sample of (x,y) with size 300. The sample is referred to as the full data, because all values of x and y are known. Then three samples with y-missing data are generated from the full data, according to the missing mechanisms MCAR, MAR and MNAR, respectively. 27 / 46

28 Result Full data MCAR MAR MNAR (Intercept) 0.08(0.06) 0.01(0.08) 0.07(0.13) 0.44(0.09) x 1.02(0.06) 1.01(0.08) 1.15(0.12) 0.70(0.09) R Adj. R Num. obs / 46

29 Methods for Dealing with Missing Data- Complete data Analysis As the name suggests, the complete-case method (also known as list-wise deletion) makes use of cases with complete data on all variables of interest in the analysis. Cases with incomplete data on one or more variables are discarded. This approach is easiest to implement since standard full data analysis can be applied without modification, and is the default in many statistical software (i.e., cases with any missing values are automatically ignored). The disadvantages include loss of precision due to a smaller sample size, and bias in complete-data summaries when the cases with missing data differ systematically from the completely observed cases (i.e., when data are not missing completely at random). 29 / 46

30 Weighted Complete Data Method The earlier complete-case strategy can potentially lead to biased summaries because the sample of observed cases may not be representative of the full sample. Another strategy reweights the sample to make it more representative. For example, if response rate is twice as likely among men as women, data from each man in the sample could receive a weight of 2 in order to make the data more representative. This strategy is commonly used in sample surveys, especially in the case of unit nonresponse, where all the survey items are missing for cases in the sample that did not participate. This method usually requires the MAR assumption. 30 / 46

31 Maximum Likelihood (ML) Method under MAR The fundamental idea behind the ML methods is conveyed by its name: find the values of the parameters that are most probable, or most likely, for the data that have actually been observed. Denote D obs as the observed data, which have the probability density p(d obs θ). Here θ is a set of the parameters of interest. Then the likelihood function L(θ D obs ) is equal to p(d obs θ), i.e. L(θ x) = p(d obs θ), and is thought of as a function of θ where the data D obs are fixed. 31 / 46

32 Maximum Likelihood Method under MAR, continued The next step is to deduce a numerical value for θ using our knowledge of L(θ x). The ML principle says we should choose an estimate of θ that maximizes the likelihood function. In other words, we choose a value of the parameter that best explains the observed data, and this value is called the ML estimate of θ. 32 / 46

33 Calculation of the ML estimates Finding the maximum can be easy or hard, depending on the form of p(d obs θ). For the normal (gaussian) distribution, θ consists of the mean µ and variance σ 2, and we can find the derivative of the log(lθ D obs )), set it equal to zero, and solve directly for µ and σ 2. But for most problems, these analytic expressions are hard to come by, and we have to use more elaborate techniques. One might use Newton-Raphson or quasi-newton algorithms to directly maximize the likelihood of the observed data. One of the most popular techniques for maximizing the likelihood function is the expectation-maximization (EM) algorithm. 33 / 46

34 Imputation-based Methods implicit modeling methods Hot deck imputation: replacing missing values by values from similar responding units in the sample. Cold deck imputation: replace a missing value of an item by a constant value from an external source. Model-based procedures: define a model for the observed data and base imputation on a draw from the posterior distribution of missing data conditional on observed data under that model. 34 / 46

35 Single Imputation Single imputation substitutes some reasonable guess (imputation) for each missing value and then perform the analysis as if there were no missing data. Mean imputation: A popular approach replaces each missing value with the unconditional mean of the observed values for a particular variable. This single-imputation approach can lead to underestimating standard errors. Additionally, this method distorts relationships between variables since it pushes the correlations between variables towards zero. 35 / 46

36 Single Imputation, continued Conditional mean imputation: For data sets with few missing variables, conditional mean imputation is an improvement on the unconditional mean approach since it replaces each missing value with the conditional mean of the variable based on other fully observed variables in the data set. Regression imputation: replace missing values by predicted values from a regression of the missing item on items observed for the unit, usually calculated from units with both observed and missing variables present. Mean imputation is a special case. Stochastic regression imputation: replace missing values by a value predicted by regression imputation plus a residual, drawn to reflect uncertainty in the predicted value. 36 / 46

37 Nearest Neighbor Hot Deck on imputing Missing Outcome Define a metric to measure distance between units, based on the values of observed covariates Choose imputed values that come from responding units close to the units with missing value. 37 / 46

38 Nearest Neighbor Hot Deck, Cont Let X = (X 1,..., X K ) be K covariates that are observable for all units, and let x i = (x i1,..., x ik ) T be the values of K covariates for a unit i for which y i is missing. Let d(i,j) be the metric between two covariates x i and x j of unit i and unit j. 38 / 46

39 Nearest Neighbor Hot Deck, Cont For the unit i, we choose an imputed value for y i from those units j that are such that (1) y j,x j1,..., x jk are observed, and (2) d(i,j) is less than some value d / 46

40 Comments on Imputation Imputation should generally be Conditional on observed variable, to reduce bias due to response, improve precision, and preserve association between missing and observed variables. Multivariate, to preserve associations between missing variables. Draws from the predictive distribution rather than means. Account for imputation uncertainty multiple imputation. 40 / 46

41 Multiple Imputation, cont Imputation: Create D imputations of the missing data, (1) (d) Y mis,..., Y mis, under a suitable model. Analysis: Analyze each of the m completed datasets in the same way. Combination: Combine the m sets of estimates and SE s using Rubin s (1987) rules. 41 / 46

42 Picture Illustration Observed D ata???? Im putation 1 2 m 42 / 46

43 Software for Multiple Imputation - SAS PROC MI implements multiple imputation by the multivariate normal model. PROC MIANALYZE takes the results of the complete-data analysis per dataset. IVEware is a SAS callable software application that implements multiple imputation using chained equations, called sequential regressions. 43 / 46

44 Software for Multiple Imputation - STATA The ice package: a user-contributed Stata package that provides multiple imputation by chained equations. 44 / 46

45 Software for Multiple Imputation - SPSS Command, MULTIPLE IMPUTATION: a part of the Missing Values module, supports multiple imputations by chained equations. Imputation and analysis can be done in a largely automatic fashion and is well integrated with the software for complete-data analysis. 45 / 46

46 Software for Multiple Imputation - R Amelia: multiple imputations based on the multivariate normal model. BaBooN: multiple imputations by chained equations. cat: multiple imputation of categorical data according to the log-linear model. kmi: a Kaplan-Meier multiple imputation, specifically designed to impute missing censoring times. mi: a chained equations approach based on Bayesian regression methods. mice: MI by the chained equations. 46 / 46

### A Basic Introduction to Missing Data

John Fox Sociology 740 Winter 2014 Outline Why Missing Data Arise Why Missing Data Arise Global or unit non-response. In a survey, certain respondents may be unreachable or may refuse to participate. Item

### Missing Data Dr Eleni Matechou

1 Statistical Methods Principles Missing Data Dr Eleni Matechou matechou@stats.ox.ac.uk References: R.J.A. Little and D.B. Rubin 2nd edition Statistical Analysis with Missing Data J.L. Schafer and J.W.

### Review of the Methods for Handling Missing Data in. Longitudinal Data Analysis

Int. Journal of Math. Analysis, Vol. 5, 2011, no. 1, 1-13 Review of the Methods for Handling Missing Data in Longitudinal Data Analysis Michikazu Nakai and Weiming Ke Department of Mathematics and Statistics

### Handling missing data in large data sets. Agostino Di Ciaccio Dept. of Statistics University of Rome La Sapienza

Handling missing data in large data sets Agostino Di Ciaccio Dept. of Statistics University of Rome La Sapienza The problem Often in official statistics we have large data sets with many variables and

### Dealing with Missing Data

Res. Lett. Inf. Math. Sci. (2002) 3, 153-160 Available online at http://www.massey.ac.nz/~wwiims/research/letters/ Dealing with Missing Data Judi Scheffer I.I.M.S. Quad A, Massey University, P.O. Box 102904

### Imputing Missing Data using SAS

ABSTRACT Paper 3295-2015 Imputing Missing Data using SAS Christopher Yim, California Polytechnic State University, San Luis Obispo Missing data is an unfortunate reality of statistics. However, there are

### MISSING DATA TECHNIQUES WITH SAS. IDRE Statistical Consulting Group

MISSING DATA TECHNIQUES WITH SAS IDRE Statistical Consulting Group ROAD MAP FOR TODAY To discuss: 1. Commonly used techniques for handling missing data, focusing on multiple imputation 2. Issues that could

### Challenges in Longitudinal Data Analysis: Baseline Adjustment, Missing Data, and Drop-out

Challenges in Longitudinal Data Analysis: Baseline Adjustment, Missing Data, and Drop-out Sandra Taylor, Ph.D. IDDRC BBRD Core 23 April 2014 Objectives Baseline Adjustment Introduce approaches Guidance

### Missing Data: Part 1 What to Do? Carol B. Thompson Johns Hopkins Biostatistics Center SON Brown Bag 3/20/13

Missing Data: Part 1 What to Do? Carol B. Thompson Johns Hopkins Biostatistics Center SON Brown Bag 3/20/13 Overview Missingness and impact on statistical analysis Missing data assumptions/mechanisms Conventional

### 2. Making example missing-value datasets: MCAR, MAR, and MNAR

Lecture 20 1. Types of missing values 2. Making example missing-value datasets: MCAR, MAR, and MNAR 3. Common methods for missing data 4. Compare results on example MCAR, MAR, MNAR data 1 Missing Data

### Handling attrition and non-response in longitudinal data

Longitudinal and Life Course Studies 2009 Volume 1 Issue 1 Pp 63-72 Handling attrition and non-response in longitudinal data Harvey Goldstein University of Bristol Correspondence. Professor H. Goldstein

### Introduction to mixed model and missing data issues in longitudinal studies

Introduction to mixed model and missing data issues in longitudinal studies Hélène Jacqmin-Gadda INSERM, U897, Bordeaux, France Inserm workshop, St Raphael Outline of the talk I Introduction Mixed models

### Handling missing data in Stata a whirlwind tour

Handling missing data in Stata a whirlwind tour 2012 Italian Stata Users Group Meeting Jonathan Bartlett www.missingdata.org.uk 20th September 2012 1/55 Outline The problem of missing data and a principled

### Missing Data. A Typology Of Missing Data. Missing At Random Or Not Missing At Random

[Leeuw, Edith D. de, and Joop Hox. (2008). Missing Data. Encyclopedia of Survey Research Methods. Retrieved from http://sage-ereference.com/survey/article_n298.html] Missing Data An important indicator

### Statistical Analysis with Missing Data

Statistical Analysis with Missing Data Second Edition RODERICK J. A. LITTLE DONALD B. RUBIN WILEY- INTERSCIENCE A JOHN WILEY & SONS, INC., PUBLICATION Contents Preface PARTI OVERVIEW AND BASIC APPROACHES

### Analyzing Structural Equation Models With Missing Data

Analyzing Structural Equation Models With Missing Data Craig Enders* Arizona State University cenders@asu.edu based on Enders, C. K. (006). Analyzing structural equation models with missing data. In G.

### Multiple Imputation for Missing Data: A Cautionary Tale

Multiple Imputation for Missing Data: A Cautionary Tale Paul D. Allison University of Pennsylvania Address correspondence to Paul D. Allison, Sociology Department, University of Pennsylvania, 3718 Locust

### Missing Data in Longitudinal Studies: To Impute or not to Impute? Robert Platt, PhD McGill University

Missing Data in Longitudinal Studies: To Impute or not to Impute? Robert Platt, PhD McGill University 1 Outline Missing data definitions Longitudinal data specific issues Methods Simple methods Multiple

### A REVIEW OF CURRENT SOFTWARE FOR HANDLING MISSING DATA

123 Kwantitatieve Methoden (1999), 62, 123-138. A REVIEW OF CURRENT SOFTWARE FOR HANDLING MISSING DATA Joop J. Hox 1 ABSTRACT. When we deal with a large data set with missing data, we have to undertake

### Imputation and Analysis. Peter Fayers

Missing Data in Palliative Care Research Imputation and Analysis Peter Fayers Department of Public Health University of Aberdeen NTNU Det medisinske fakultet Missing data Missing data is a major problem

### A Mixed Model Approach for Intent-to-Treat Analysis in Longitudinal Clinical Trials with Missing Values

Methods Report A Mixed Model Approach for Intent-to-Treat Analysis in Longitudinal Clinical Trials with Missing Values Hrishikesh Chakraborty and Hong Gu March 9 RTI Press About the Author Hrishikesh Chakraborty,

### Overview. Longitudinal Data Variation and Correlation Different Approaches. Linear Mixed Models Generalized Linear Mixed Models

Overview 1 Introduction Longitudinal Data Variation and Correlation Different Approaches 2 Mixed Models Linear Mixed Models Generalized Linear Mixed Models 3 Marginal Models Linear Models Generalized Linear

### Analysis of Longitudinal Data with Missing Values.

Analysis of Longitudinal Data with Missing Values. Methods and Applications in Medical Statistics. Ingrid Garli Dragset Master of Science in Physics and Mathematics Submission date: June 2009 Supervisor:

### MISSING DATA IMPUTATION IN CARDIAC DATA SET (SURVIVAL PROGNOSIS)

MISSING DATA IMPUTATION IN CARDIAC DATA SET (SURVIVAL PROGNOSIS) R.KAVITHA KUMAR Department of Computer Science and Engineering Pondicherry Engineering College, Pudhucherry, India DR. R.M.CHADRASEKAR Professor,

### Missing Data & How to Deal: An overview of missing data. Melissa Humphries Population Research Center

Missing Data & How to Deal: An overview of missing data Melissa Humphries Population Research Center Goals Discuss ways to evaluate and understand missing data Discuss common missing data methods Know

### Combining Multiple Imputation and Inverse Probability Weighting

Combining Multiple Imputation and Inverse Probability Weighting Shaun Seaman 1, Ian White 1, Andrew Copas 2,3, Leah Li 4 1 MRC Biostatistics Unit, Cambridge 2 MRC Clinical Trials Unit, London 3 UCL Research

### Modern Methods for Missing Data

Modern Methods for Missing Data Paul D. Allison, Ph.D. Statistical Horizons LLC www.statisticalhorizons.com 1 Introduction Missing data problems are nearly universal in statistical practice. Last 25 years

### How to choose an analysis to handle missing data in longitudinal observational studies

How to choose an analysis to handle missing data in longitudinal observational studies ICH, 25 th February 2015 Ian White MRC Biostatistics Unit, Cambridge, UK Plan Why are missing data a problem? Methods:

### Nonrandomly Missing Data in Multiple Regression Analysis: An Empirical Comparison of Ten Missing Data Treatments

Brockmeier, Kromrey, & Hogarty Nonrandomly Missing Data in Multiple Regression Analysis: An Empirical Comparison of Ten s Lantry L. Brockmeier Jeffrey D. Kromrey Kristine Y. Hogarty Florida A & M University

### Workpackage 11 Imputation and Non-Response. Deliverable 11.2

Workpackage 11 Imputation and Non-Response Deliverable 11.2 2004 II List of contributors: Seppo Laaksonen, Statistics Finland; Ueli Oetliker, Swiss Federal Statistical Office; Susanne Rässler, University

### Item Imputation Without Specifying Scale Structure

Original Article Item Imputation Without Specifying Scale Structure Stef van Buuren TNO Quality of Life, Leiden, The Netherlands University of Utrecht, The Netherlands Abstract. Imputation of incomplete

### Sensitivity Analysis in Multiple Imputation for Missing Data

Paper SAS270-2014 Sensitivity Analysis in Multiple Imputation for Missing Data Yang Yuan, SAS Institute Inc. ABSTRACT Multiple imputation, a popular strategy for dealing with missing values, usually assumes

### Statistical modelling with missing data using multiple imputation. Session 4: Sensitivity Analysis after Multiple Imputation

Statistical modelling with missing data using multiple imputation Session 4: Sensitivity Analysis after Multiple Imputation James Carpenter London School of Hygiene & Tropical Medicine Email: james.carpenter@lshtm.ac.uk

### Bayesian Approaches to Handling Missing Data

Bayesian Approaches to Handling Missing Data Nicky Best and Alexina Mason BIAS Short Course, Jan 30, 2012 Lecture 1. Introduction to Missing Data Bayesian Missing Data Course (Lecture 1) Introduction to

### Missing Data Techniques for Structural Equation Modeling

Journal of Abnormal Psychology Copyright 2003 by the American Psychological Association, Inc. 2003, Vol. 112, No. 4, 545 557 0021-843X/03/\$12.00 DOI: 10.1037/0021-843X.112.4.545 Missing Data Techniques

### Health 2011 Survey: An overview of the design, missing data and statistical analyses examples

Health 2011 Survey: An overview of the design, missing data and statistical analyses examples Tommi Härkänen Department of Health, Functional Capacity and Welfare The National Institute for Health and

### Missing Data. Katyn & Elena

Missing Data Katyn & Elena What to do with Missing Data Standard is complete case analysis/listwise dele;on ie. Delete cases with missing data so only complete cases are le> Two other popular op;ons: Mul;ple

### Missing data: the hidden problem

white paper Missing data: the hidden problem Draw more valid conclusions with SPSS Missing Data Analysis white paper Missing data: the hidden problem 2 Just about everyone doing analysis has some missing

### Missing Data. Paul D. Allison INTRODUCTION

4 Missing Data Paul D. Allison INTRODUCTION Missing data are ubiquitous in psychological research. By missing data, I mean data that are missing for some (but not all) variables and for some (but not all)

### Dr James Roger. GlaxoSmithKline & London School of Hygiene and Tropical Medicine.

American Statistical Association Biopharm Section Monthly Webinar Series: Sensitivity analyses that address missing data issues in Longitudinal studies for regulatory submission. Dr James Roger. GlaxoSmithKline

### HANDLING DROPOUT AND WITHDRAWAL IN LONGITUDINAL CLINICAL TRIALS

HANDLING DROPOUT AND WITHDRAWAL IN LONGITUDINAL CLINICAL TRIALS Mike Kenward London School of Hygiene and Tropical Medicine Acknowledgements to James Carpenter (LSHTM) Geert Molenberghs (Universities of

### Dealing with Missing Data

Dealing with Missing Data Roch Giorgi email: roch.giorgi@univ-amu.fr UMR 912 SESSTIM, Aix Marseille Université / INSERM / IRD, Marseille, France BioSTIC, APHM, Hôpital Timone, Marseille, France January

### Analyzing Intervention Effects: Multilevel & Other Approaches. Simplest Intervention Design. Better Design: Have Pretest

Analyzing Intervention Effects: Multilevel & Other Approaches Joop Hox Methodology & Statistics, Utrecht Simplest Intervention Design R X Y E Random assignment Experimental + Control group Analysis: t

### Dealing with missing data: Key assumptions and methods for applied analysis

Technical Report No. 4 May 6, 2013 Dealing with missing data: Key assumptions and methods for applied analysis Marina Soley-Bori msoley@bu.edu This paper was published in fulfillment of the requirements

### PATTERN MIXTURE MODELS FOR MISSING DATA. Mike Kenward. London School of Hygiene and Tropical Medicine. Talk at the University of Turku,

PATTERN MIXTURE MODELS FOR MISSING DATA Mike Kenward London School of Hygiene and Tropical Medicine Talk at the University of Turku, April 10th 2012 1 / 90 CONTENTS 1 Examples 2 Modelling Incomplete Data

### Missing data in randomized controlled trials (RCTs) can

EVALUATION TECHNICAL ASSISTANCE BRIEF for OAH & ACYF Teenage Pregnancy Prevention Grantees May 2013 Brief 3 Coping with Missing Data in Randomized Controlled Trials Missing data in randomized controlled

### A Review of Methods for Missing Data

Educational Research and Evaluation 1380-3611/01/0704-353\$16.00 2001, Vol. 7, No. 4, pp. 353±383 # Swets & Zeitlinger A Review of Methods for Missing Data Therese D. Pigott Loyola University Chicago, Wilmette,

### On Treatment of the Multivariate Missing Data

On Treatment of the Multivariate Missing Data Peter J. Foster, Ahmed M. Mami & Ali M. Bala First version: 3 September 009 Research Report No. 3, 009, Probability and Statistics Group School of Mathematics,

### Data Cleaning and Missing Data Analysis

Data Cleaning and Missing Data Analysis Dan Merson vagabond@psu.edu India McHale imm120@psu.edu April 13, 2010 Overview Introduction to SACS What do we mean by Data Cleaning and why do we do it? The SACS

### Introduction to latent variable models

Introduction to latent variable models lecture 1 Francesco Bartolucci Department of Economics, Finance and Statistics University of Perugia, IT bart@stat.unipg.it Outline [2/24] Latent variables and their

### Missing data are ubiquitous in clinical research.

Advanced Statistics: Missing Data in Clinical Research Part 1: An Introduction and Conceptual Framework Jason S. Haukoos, MD, MS, Craig D. Newgard, MD, MPH Abstract Missing data are commonly encountered

ALLISON 1 TABLE OF CONTENTS 1. INTRODUCTION... 3 2. ASSUMPTIONS... 6 MISSING COMPLETELY AT RANDOM (MCAR)... 6 MISSING AT RANDOM (MAR)... 7 IGNORABLE... 8 NONIGNORABLE... 8 3. CONVENTIONAL METHODS... 10

### Missing Data Sensitivity Analysis of a Continuous Endpoint An Example from a Recent Submission

Missing Data Sensitivity Analysis of a Continuous Endpoint An Example from a Recent Submission Arno Fritsch Clinical Statistics Europe, Bayer November 21, 2014 ASA NJ Chapter / Bayer Workshop, Whippany

### Title: Categorical Data Imputation Using Non-Parametric or Semi-Parametric Imputation Methods

Masters by Coursework and Research Report Mathematical Statistics School of Statistics and Actuarial Science Title: Categorical Data Imputation Using Non-Parametric or Semi-Parametric Imputation Methods

### Re-analysis using Inverse Probability Weighting and Multiple Imputation of Data from the Southampton Women s Survey

Re-analysis using Inverse Probability Weighting and Multiple Imputation of Data from the Southampton Women s Survey MRC Biostatistics Unit Institute of Public Health Forvie Site Robinson Way Cambridge

### Missing Data: Our View of the State of the Art

Psychological Methods Copyright 2002 by the American Psychological Association, Inc. 2002, Vol. 7, No. 2, 147 177 1082-989X/02/\$5.00 DOI: 10.1037//1082-989X.7.2.147 Missing Data: Our View of the State

### How To Use A Monte Carlo Study To Decide On Sample Size and Determine Power

How To Use A Monte Carlo Study To Decide On Sample Size and Determine Power Linda K. Muthén Muthén & Muthén 11965 Venice Blvd., Suite 407 Los Angeles, CA 90066 Telephone: (310) 391-9971 Fax: (310) 391-8971

### An introduction to modern missing data analyses

Journal of School Psychology 48 (2010) 5 37 An introduction to modern missing data analyses Amanda N. Baraldi, Craig K. Enders Arizona State University, United States Received 19 October 2009; accepted

### A Review of Missing Data Treatment Methods

A Review of Missing Data Treatment Methods Liu Peng, Lei Lei Department of Information Systems, Shanghai University of Finance and Economics, Shanghai, 200433, P.R. China ABSTRACT Missing data is a common

### Imputing Attendance Data in a Longitudinal Multilevel Panel Data Set

Imputing Attendance Data in a Longitudinal Multilevel Panel Data Set April 2015 SHORT REPORT Baby FACES 2009 This page is left blank for double-sided printing. Imputing Attendance Data in a Longitudinal

### Imputation of missing data under missing not at random assumption & sensitivity analysis

Imputation of missing data under missing not at random assumption & sensitivity analysis S. Jolani Department of Methodology and Statistics, Utrecht University, the Netherlands Advanced Multiple Imputation,

### Missing Data in Survival Analysis and Results from the MESS Trial

Missing Data in Survival Analysis and Results from the MESS Trial J. K. Rogers J. L. Hutton K. Hemming Department of Statistics University of Warwick Research Students Conference, 2008 Outline Background

### Best Practices for Missing Data Management in Counseling Psychology

Journal of Counseling Psychology 2010 American Psychological Association 2010, Vol. 57, No. 1, 1 10 0022-0167/10/\$12.00 DOI: 10.1037/a0018082 Best Practices for Missing Data Management in Counseling Psychology

### arxiv:1301.2490v1 [stat.ap] 11 Jan 2013

The Annals of Applied Statistics 2012, Vol. 6, No. 4, 1814 1837 DOI: 10.1214/12-AOAS555 c Institute of Mathematical Statistics, 2012 arxiv:1301.2490v1 [stat.ap] 11 Jan 2013 ADDRESSING MISSING DATA MECHANISM

### Applied Missing Data Analysis in the Health Sciences. Statistics in Practice

Brochure More information from http://www.researchandmarkets.com/reports/2741464/ Applied Missing Data Analysis in the Health Sciences. Statistics in Practice Description: A modern and practical guide

### A Pseudo Nearest-Neighbor Approach for Missing Data Recovery on Gaussian Random Data Sets

University of Nebraska at Omaha DigitalCommons@UNO Computer Science Faculty Publications Department of Computer Science -2002 A Pseudo Nearest-Neighbor Approach for Missing Data Recovery on Gaussian Random

### SPSS TRAINING SESSION 3 ADVANCED TOPICS (PASW STATISTICS 17.0) Sun Li Centre for Academic Computing lsun@smu.edu.sg

SPSS TRAINING SESSION 3 ADVANCED TOPICS (PASW STATISTICS 17.0) Sun Li Centre for Academic Computing lsun@smu.edu.sg IN SPSS SESSION 2, WE HAVE LEARNT: Elementary Data Analysis Group Comparison & One-way

### Data fusion with international large scale assessments: a case study using the OECD PISA and TALIS surveys

Kaplan and McCarty Large-scale Assessments in Education 2013, 1:6 RESEARCH Open Access Data fusion with international large scale assessments: a case study using the OECD PISA and TALIS surveys David Kaplan

### Comparison of Imputation Methods in the Survey of Income and Program Participation

Comparison of Imputation Methods in the Survey of Income and Program Participation Sarah McMillan U.S. Census Bureau, 4600 Silver Hill Rd, Washington, DC 20233 Any views expressed are those of the author

### Missing data and net survival analysis Bernard Rachet

Workshop on Flexible Models for Longitudinal and Survival Data with Applications in Biostatistics Warwick, 27-29 July 2015 Missing data and net survival analysis Bernard Rachet General context Population-based,

### Reject Inference in Credit Scoring. Jie-Men Mok

Reject Inference in Credit Scoring Jie-Men Mok BMI paper January 2009 ii Preface In the Master programme of Business Mathematics and Informatics (BMI), it is required to perform research on a business

### Using Medical Research Data to Motivate Methodology Development among Undergraduates in SIBS Pittsburgh

Using Medical Research Data to Motivate Methodology Development among Undergraduates in SIBS Pittsburgh Megan Marron and Abdus Wahed Graduate School of Public Health Outline My Experience Motivation for

### CHOOSING APPROPRIATE METHODS FOR MISSING DATA IN MEDICAL RESEARCH: A DECISION ALGORITHM ON METHODS FOR MISSING DATA

CHOOSING APPROPRIATE METHODS FOR MISSING DATA IN MEDICAL RESEARCH: A DECISION ALGORITHM ON METHODS FOR MISSING DATA Hatice UENAL Institute of Epidemiology and Medical Biometry, Ulm University, Germany

### WHAT DO WE DO WITH MISSING DATA?SOME OPTIONS FOR ANALYSIS OF INCOMPLETE DATA

Annu. Rev. Public Health 2004. 25:99 117 doi: 10.1146/annurev.publhealth.25.102802.124410 Copyright c 2004 by Annual Reviews. All rights reserved WHAT DO WE DO WITH MISSING DATA?SOME OPTIONS FOR ANALYSIS

### APPLIED MISSING DATA ANALYSIS

APPLIED MISSING DATA ANALYSIS Craig K. Enders Series Editor's Note by Todd D. little THE GUILFORD PRESS New York London Contents 1 An Introduction to Missing Data 1 1.1 Introduction 1 1.2 Chapter Overview

### How to Use a Monte Carlo Study to Decide on Sample Size and Determine Power

STRUCTURAL EQUATION MODELING, 9(4), 599 620 Copyright 2002, Lawrence Erlbaum Associates, Inc. TEACHER S CORNER How to Use a Monte Carlo Study to Decide on Sample Size and Determine Power Linda K. Muthén

### Bayesian Statistics in One Hour. Patrick Lam

Bayesian Statistics in One Hour Patrick Lam Outline Introduction Bayesian Models Applications Missing Data Hierarchical Models Outline Introduction Bayesian Models Applications Missing Data Hierarchical

### IBM SPSS Missing Values 22

IBM SPSS Missing Values 22 Note Before using this information and the product it supports, read the information in Notices on page 23. Product Information This edition applies to version 22, release 0,

### Fundamental Probability and Statistics

Fundamental Probability and Statistics "There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are

### Discussion. Seppo Laaksonen 1. 1. Introduction

Journal of Official Statistics, Vol. 23, No. 4, 2007, pp. 467 475 Discussion Seppo Laaksonen 1 1. Introduction Bjørnstad s article is a welcome contribution to the discussion on multiple imputation (MI)

### Imputation of missing network data: Some simple procedures

Imputation of missing network data: Some simple procedures Mark Huisman Dept. of Psychology University of Groningen Abstract Analysis of social network data is often hampered by non-response and missing

### A Review of Methods. for Dealing with Missing Data. Angela L. Cool. Texas A&M University 77843-4225

Missing Data 1 Running head: DEALING WITH MISSING DATA A Review of Methods for Dealing with Missing Data Angela L. Cool Texas A&M University 77843-4225 Paper presented at the annual meeting of the Southwest

### Introduction to Multivariate Models: Modeling Multivariate Outcomes with Mixed Model Repeated Measures Analyses

Introduction to Multivariate Models: Modeling Multivariate Outcomes with Mixed Model Repeated Measures Analyses Applied Multilevel Models for Cross Sectional Data Lecture 11 ICPSR Summer Workshop University

### Longitudinal Studies, The Institute of Education, University of London. Square, London, EC1 OHB, U.K. Email: R.D.Wiggins@city.ac.

A comparative evaluation of currently available software remedies to handle missing data in the context of longitudinal design and analysis. Wiggins, R.D 1., Ely, M 2. & Lynch, K. 3 1 Department of Sociology,

### What s Missing? Handling Missing Data with SAS

What s Missing? Handling Missing Data with SAS Timothy B. Gravelle Principal Scientist & Director, Insights Lab September 13, 2013 2000-2013 PriceMetrix Inc. Patents granted and pending. Missing data Survey

### Service courses for graduate students in degree programs other than the MS or PhD programs in Biostatistics.

Course Catalog In order to be assured that all prerequisites are met, students must acquire a permission number from the education coordinator prior to enrolling in any Biostatistics course. Courses are

### CHAPTER 6 EXAMPLES: GROWTH MODELING AND SURVIVAL ANALYSIS

Examples: Growth Modeling And Survival Analysis CHAPTER 6 EXAMPLES: GROWTH MODELING AND SURVIVAL ANALYSIS Growth models examine the development of individuals on one or more outcome variables over time.

### Note on the EM Algorithm in Linear Regression Model

International Mathematical Forum 4 2009 no. 38 1883-1889 Note on the M Algorithm in Linear Regression Model Ji-Xia Wang and Yu Miao College of Mathematics and Information Science Henan Normal University

### Assignments Analysis of Longitudinal data: a multilevel approach

Assignments Analysis of Longitudinal data: a multilevel approach Frans E.S. Tan Department of Methodology and Statistics University of Maastricht The Netherlands Maastricht, Jan 2007 Correspondence: Frans

### Module 14: Missing Data Stata Practical

Module 14: Missing Data Stata Practical Jonathan Bartlett & James Carpenter London School of Hygiene & Tropical Medicine www.missingdata.org.uk Supported by ESRC grant RES 189-25-0103 and MRC grant G0900724

### IBM SPSS Missing Values 20

IBM SPSS Missing Values 20 Note: Before using this information and the product it supports, read the general information under Notices on p. 87. This edition applies to IBM SPSS Statistics 20 and to all

### Introduction to Longitudinal Data Analysis

Introduction to Longitudinal Data Analysis Longitudinal Data Analysis Workshop Section 1 University of Georgia: Institute for Interdisciplinary Research in Education and Human Development Section 1: Introduction

### Missing Data in Educational Research: A Review of Reporting Practices and Suggestions for Improvement

Review of Educational Research Winter 2004, Vol. 74, No. 4, pp. 525-556 Missing Data in Educational Research: A Review of Reporting Practices and Suggestions for Improvement James L. Peugh University of

### L10: Probability, statistics, and estimation theory

L10: Probability, statistics, and estimation theory Review of probability theory Bayes theorem Statistics and the Normal distribution Least Squares Error estimation Maximum Likelihood estimation Bayesian

### Electronic Theses and Dissertations UC Riverside

Electronic Theses and Dissertations UC Riverside Peer Reviewed Title: Bayesian and Non-parametric Approaches to Missing Data Analysis Author: Yu, Yao Acceptance Date: 01 Series: UC Riverside Electronic

### Analysis of Incomplete Survey Data Multiple Imputation via Bayesian Bootstrap Predictive Mean Matching

Analysis of Incomplete Survey Data Multiple Imputation via Bayesian Bootstrap Predictive Mean Matching Dissertation zur Erlangung des akademischen Grades eines Doktors der Sozial- und Wirtschaftswissenschaften

### (Brief rest break when appealing) Please silence your cell phones and pagers. Invite brief questions of clarification.

The Ugly, the Bad, and the Good of Missing and Dropout Data in Analysis and Sample Size Selection Keith E. Muller Professor and Director of the Division of Biostatistics, Epidemiology and Health Policy

### Quantitative Methods Workshop. Graphical Methods for Investigating Missing Data

Quantitative Methods Workshop Graphical Methods for Investigating Missing Data Graeme Hutcheson School of Education University of Manchester missing data data imputation missing data Data sets with missing