# An Introduction to Sampling

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 An Introduction to Sampling Sampling is the process of selecting a subset of units from the population. We use sampling formulas to determine how many to select because it is based on the characteristics of this sample that we make inferences about the population. In preparing to take a sample, there many questions we might have, including: Can we make procedural errors that influence the results, but are not related to the sample itself? Can we make errors in our sampling? How can we determine the size and the accuracy of the sample result? SYSTEMATIC ERRORS (NON-SAMPLING ERRORS) Systematic errors result from decisions that bias the sample selection or response to your survey. Four common mistakes are made: 1. Population Specification Error: This error is one of not understanding who you should be surveying. As a simple example, imagine you are preparing a survey about the consumption of breakfast cereals. Who do you survey? It might be the entire family, the mother, or the children. The family consumes cereal, the mother purchases, and the children influence her choice. 2. Sample Frame Error: A frame error occurs when the wrong sub-population is specified from which the sample is drawn. A classic frame error occurred in predicting the 1936 presidential election between Roosevelt and Landon. The sample frame used was from car registrations and telephone directories. In 1936, car and telephone owners were largely Republicans. While the results may have reflected the sample, the predictions were not accurate for the US as a whole and the results wrongly predicted a Republican victory. 3. Selection Error: Selection error results when the respondents self select their participation... those who are interested respond. Selection error can be controlled by going extra lengths to get participation. Typical steps include initiating pre-survey contact requesting cooperation, actual surveying, post survey follow-up if a response is not received, a second survey request, and finally interviews using an alternate modes such as telephone or person to person. 4. Non-Response: Non response errors occur when non-respondents are different than those who respond. This may occur because either the potential respondent was not contacted (they did check their ) or they refused to respond (they were all grumpy old men or beautiful young women afraid of strangers). Again, the extent of this non-response error can be checked through follow-up surveys using alternate modes. An Introduction to Sampling 1

2 NON-SYSTEMATIC ERRORS (SAMPLING ERRORS) Sampling errors occur because of variation in the number or representativeness of the sample that responds. Sampling errors can be controlled by (1) Careful sample designs, (2) Large samples, and (3) Multiple contacts to assure representative response. Two types of samples may be drawn, a probability sample where every person in the sample has an equal and known probability of being selected, and a non-probability sample where the probability of a person being selected is unknown. Non-probability samples include quota samples, referral samples, and convenience samples. A quota sample assures that various subgroups of the population are represented on relevant sample characteristics. The quota sample does not use population proportions. For example a quota sample may be used to make sure you have at least 35 people who have an income more than \$250,000. Respondents from group would rarely be interviewed because of their small incidence in the population as a whole. A referral sample is used to locate a population of rare individuals by referral. Locating 100 adult croquet players may be difficult were it not by referral. Convenience samples are based on convenience and may include members of affiliation groups, interest groups, or random intercepts on your website. The objective is to collect as much data as possible, regardless of where they come from. Probability samples include simple random samples, systematic samples, and stratified samples. A simple random sample occurs where every element has a known and equal probability of being selected. A true random sample is rarely used because we rarely have a sample frame that lists every person we could sample. A systematic sample occurs all potential respondents have a known and equal chance of being selected. Typically a systematic sample would select every nth person from the list of potential respondents. For example, a systematic sample of 400 customers (out of the 3000 total customers) would be conducted by computing a respondent selection frequency (N/n) = 3000/400 = 7.5. Then this number is rounded to 8 and a random number is selected from 1-8 (suppose the result is 3). We would select a systematic sample by first selecting the third customer on the list and then every 8th thereafter. This will form a simple random sample of respondents if the customer list is not systematically ordered in some way. A stratified sample is sometimes desirable if the population is to be broken up into different groups based on one or more characteristics of the population. In this case, the strata are identified. Strata may defined as any groups: Credit card users Vs noncredit card users, by gender, age, industry, purchasers Vs non-purchasers, current customers Vs past customers, etc. Once the strata are identified, a simple random sample is drawn within each strata. Once the survey is completed, the strata are then weighted back to the population proportions. An Introduction to Sampling 2

3 Calculating Sample Size How many people do you need to interview to get results representative of the target population with the level of confidence that you are willing to accept? Given an existing sample, what is the level of precision you now have? The answer to these questions can be found using a sample size table and depends on the degree of sampling precision and accuracy you require. Computing sample size is based on the confidence interval and the confidence level. ESTIMATING SAMPLE SIZE Given the sampling methods discussed above, the final sample determination is that how many should be sampled? The most common method of sample size determination is that based on proportions. For example, suppose we are preparing for the winter Olympics and are interested in estimating the proportion of out of state skiers that took at least one over night trip. We might use this number of people that would consider traveling to the Olympics. In this case, the sample size is estimated using proportions. sp = (p/(1-p)/ n) where p is the proportion of out of state skiers that took at least one over night trip. The most conservative number for this proportion is.50 and if the desired accuracy was.05 and the formula would appear as: (Number of Standard Errors) 2 * ((proportion) * (1-proportion)) / (Accuracy) (1+((Number of Standard Errors) 2 * (proportion) * (1-proportion)) / (Accuracy) - 1) / (the proportion size) While this formula is easily entered into a spreadsheet, this formula results in the following sample size determination table. An Introduction to Sampling 3

4 Table 1: Sample Size Lookup Table for 95% Confidence Sample Size Variability Proportions 50/50% 40/60% 30/70% 20/80% 90/10% 95/5% * This table is compute using the following formula: CELLS = Ranges of Error (+ / - %) for a given sample size x expected proportions of response variable COLUMNS = Expected response proportion (Variable proportion) ROWS = Sample Size categories EXAMPLE: In a product usage study where the expected product usage incidence rate is 30%, a sample of 500 will yield a precision of +/- 4.1 percentage points at the 95% confidence level. (Number of Standard Errors) 2 * ((proportion)*(1-proportion)) / (Accuracy) (1+((Number of Standard Errors) 2 * ((proportion)*(1-proportion)) / (Accuracy)-1) / (the population size) This formula is easily entered into a spreadsheet, to compute a sample size determination table. Sample Size Terminology The following is an Edited version of Inside the paper s election polls, an article by Elsa McDowell that appeared in The Charleston Post and Courier, November 8, 2002: The beauty of... election polls is that they are straightforward. They use statistical formulae to estimate how many people will vote one way and how many will vote another. No spin. No qualifying clauses to muddy the picture. An Introduction to Sampling 4

### Sampling & Sample Size Estimation

Sampling & Sample Size Estimation Moazzam Ali MD, PhD, MPH Department of Reproductive Health and Research World Health Organization Geneva, Switzerland Presented at: GFMER September 16, 2014 Topics to

### A GUIDE TO SAMPLING & STATISTICAL RELIABILITY

July 2009 Technical Note 5 A GUIDE TO SAMPLING & STATISTICAL RELIABILITY The word survey is used most often to describe a method of gathering information from a sample of individuals. This sample is usually

### 1) Overview 2) Sample or Census 3) The Sampling Design Process i. Define the Target Population ii. Determine the Sampling Frame iii.

1) Overview 2) Sample or Census 3) The Sampling Design Process i. Define the Target Population ii. Determine the Sampling Frame iii. Select a Sampling Technique iv. Determine the Sample Size v. Execute

### These days, surveys are used everywhere and for many reasons. For example, surveys are commonly used to track the following:

The previous handout provided an overview of study designs. The two broad classifications discussed were randomized experiments and observational studies. In this handout, we will briefly introduce a specific

### Survey Process White Paper Series Five Steps in Creating a Survey Sampling Plan

Survey Process White Paper Series Five Steps in Creating a Survey Sampling Plan POLARIS MARKETING RESEARCH, INC. 1455 LINCOLN PARKWAY, SUITE 320 ATLANTA, GEORGIA 30346 404.816.0353 www.polarismr.com ii

### 5. {Boat show narrative} Specify who/what the units are in this study. ANSWER: THE UNITS ARE THE BOAT SHOW PARTICIPANTS.

Quiz CHAPTER 4 Name: 1. What is the most important advantage of using a randomized experiment vs. an observational study, in terms of the statistical results? ANSWER: RANDOMIZED EXPERIMENTS, UNLIKE OBSERVATIONAL

### DETERMINING SURVEY SAMPLE SIZE A SIMPLE PLAN

DETERMINING SURVEY SAMPLE SIZE A SIMPLE PLAN Prepared by Market Directions Market Directions B O S T O N 617-323-1862 800-475-9808 www.marketdirectionsmr.com info@marketdirectionsmr.com DETERMING SAMPLE

### Sampling: Design and Procedures

Chapter Eleven Sampling: Design and Procedures 11-1 Brand name change and re-position Coke to New Coke Legend to Lenovo (2003) Panasonic, National, Technic all to Panasonic Vegemite to isnack 2.0 (social

### MUHLENBERG COLLEGE /MORNING CALL. 2008 Presidential Tracking Poll

MUHLENBERG COLLEGE /MORNING CALL 2008 Presidential Tracking Poll RELEASE #20 October 16, 2008 FIELDING PERIOD October 11-15, 2008 SAMPLE 595 Likely Voters in Pennsylvania MARGIN OF ERROR - +/- 4.0% at

### Why Sample? Why not study everyone? Debate about Census vs. sampling

Sampling Why Sample? Why not study everyone? Debate about Census vs. sampling Problems in Sampling? What problems do you know about? What issues are you aware of? What questions do you have? Key Sampling

### POLI 300 Handout #2 N. R. Miller RANDOM SAMPLING. Key Definitions Pertaining to Sampling

POLI 300 Handout #2 N. R. Miller Key Definitions Pertaining to Sampling RANDOM SAMPLING 1. Population: the set of units (in survey research, usually individuals or households), N in number, that are to

### Chapter 19: Sampling

Chapter 19: Sampling Context................................................................... 2 Terminology................................................................ 3 Some basics 4 Population

### FLORIDA: TRUMP WIDENS LEAD OVER RUBIO

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, March 14, Contact: PATRICK MURRAY 732-979-6769

### Sample Surveys. The two most typical sources of bias are selection bias and non-response bias.

Sample Surveys In this class we will consider the problem of sampling from a finite population. This is usually referred to as a survey. The goal of the survey is to learn about some parameters of a population,

### Sampling: Design and Procedures

MBACATÓLICA JAN/APRIL 2006 Marketing Research Fernando S. Machado Week 6 Sampling: Design and Procedures Sampling: Sample Size Determination Data Preparation 1 Sampling: Design and Procedures The Sampling

### MARYLAND: CLINTON LEADS SANDERS BY 25

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Thursday, 21, Contact: PATRICK MURRAY 732-979-6769

### Western New England University Polling Institute

WESTERN NEW ENGLAND UNIVERSITY Western New England University Polling Institute Massachusetts Statewide Telephone Survey September 20-28, 2014 Dr. Tim Vercellotti For Immediate Release TABLES Next, please

### TEXAS: CRUZ, CLINTON LEAD PRIMARIES

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Thursday, 25, Contact: PATRICK MURRAY 732-979-6769

### Appendix Methodology and Statistics

Appendix Methodology and Statistics Introduction Science and Engineering Indicators (SEI) contains data compiled from a variety of sources. This appendix explains the methodological and statistical criteria

### MICHIGAN: TRUMP, CLINTON IN FRONT

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, 7, Contact: PATRICK MURRAY 732-979-6769

### VIRGINIA: TRUMP, CLINTON LEAD PRIMARIES

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Thursday, 25, Contact: PATRICK MURRAY 732-979-6769

### USING SAMPLING TO ASSESS LIBRARY COLLECTIONS

USING SAMPLING TO ASSESS LIBRARY COLLECTIONS by Jim Self Director, Management Information Services University of Virginia Library December 2001 self@virginia.edu This document is designed to demonstrate

### Statistical & Technical Team

Statistical & Technical Team A Practical Guide to Sampling This guide is brought to you by the Statistical and Technical Team, who form part of the VFM Development Team. They are responsible for advice

### Introduction to Sampling. Dr. Safaa R. Amer. Overview. for Non-Statisticians. Part II. Part I. Sample Size. Introduction.

Introduction to Sampling for Non-Statisticians Dr. Safaa R. Amer Overview Part I Part II Introduction Census or Sample Sampling Frame Probability or non-probability sample Sampling with or without replacement

### Mind on Statistics. Chapter 10

Mind on Statistics Chapter 10 Section 10.1 Questions 1 to 4: Some statistical procedures move from population to sample; some move from sample to population. For each of the following procedures, determine

### ALABAMA and OKLAHOMA: TRUMP LEADS IN BOTH CLINTON LEADS IN AL, SANDERS IN OK

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, February 29, 2016 Contact: PATRICK

### Sampling Procedures Y520. Strategies for Educational Inquiry. Robert S Michael

Sampling Procedures Y520 Strategies for Educational Inquiry Robert S Michael RSMichael 2-1 Terms Population (or universe) The group to which inferences are made based on a sample drawn from the population.

### Sample Size Determination

Sample Size Determination Population A: 10,000 Population B: 5,000 Sample 10% Sample 15% Sample size 1000 Sample size 750 The process of obtaining information from a subset (sample) of a larger group (population)

### Lecture #9 Tuesday, September 20, 2016 Textbook: Section 4.3, 5.1, 5.2, 5.3

STATISTICS 200 Lecture #9 Tuesday, September 20, 2016 Textbook: Section 4.3, 5.1, 5.2, 5.3 Objectives: Understand Simpson s paradox: What causes it, why it s surprising Contrast statistical significance

### Need for Sampling. Very large populations Destructive testing Continuous production process

Chapter 4 Sampling and Estimation Need for Sampling Very large populations Destructive testing Continuous production process The objective of sampling is to draw a valid inference about a population. 4-

### Carolyn Anderson & Youngshil Paek (Slides created by Shuai Sam Wang) Department of Educational Psychology University of Illinois at Urbana-Champaign

Carolyn Anderson & Youngshil Paek (Slides created by Shuai Sam Wang) Department of Educational Psychology University of Illinois at Urbana-Champaign Key Points 1. Data 2. Variable 3. Types of data 4. Define

### Experimental Design. How to Handle Confounding?

Controlled Experiment: Researchers assign treatment and control groups and examine any resulting changes in the response variable. (cause-and-effect conclusion) How to Handle Confounding? Controlled Experiments:

### The Margin of Error for Differences in Polls

The Margin of Error for Differences in Polls Charles H. Franklin University of Wisconsin, Madison October 27, 2002 (Revised, February 9, 2007) The margin of error for a poll is routinely reported. 1 But

### Sampling. General 2 Population vs sample... 3 Key ideas... 4 Population parameter... 5 Sample and statistic... 6

Sampling General 2 Population vs sample........................................................ 3 Key ideas................................................................ 4 Population parameter........................................................

### APPENDIX A: SURVEY METHODOLOGY

55 APPENDIX A: SURVEY METHODOLOGY The survey was conducted by telephone with a national sample of adults (18 years of age or older) living in all 50 U.S. states and the District of Columbia. The results

### OHIO: KASICH, TRUMP IN GOP SQUEAKER; CLINTON LEADS IN DEM RACE

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, 14, Contact: PATRICK MURRAY 732-979-6769

### RECOMMENDED CITATION: Pew Research Center, January, 2016, Republican Primary Voters: More Conservative than GOP General Election Voters

NUMBERS, FACTS AND TRENDS SHAPING THE WORLD FOR RELEASE JANUARY 28, 2016 FOR MEDIA OR OTHER INQUIRIES: Carroll Doherty, Director of Political Research Jocelyn Kiley, Associate Director, Research Bridget

### Prof. Kate Calder. It may be impossible to collect information about every member of the population. Time Cost Convenience

Sampling Design The idea of sampling: We want to say something about a population - the entire group of individuals that we want information about. To get at this we take a sample - a part of the population

### Newsweek Poll Election 2008 One Year Out Princeton Survey Research Associates International. Final Topline Results (11/2/07)

Newsweek Poll Election 2008 One Year Out Princeton Survey Research Associates International Final Topline Results (11/2/07) N = 1,002 registered voters Margin of error: plus or minus 4 Interviewing dates:

### primary data (collect the data yourself) secondary data (use data collected by others)

Slide 3.1 Chapter 9: Data collection and sampling methods Data collection primary data (collect the data yourself) secondary data (use data collected by others) Examine secondary sources first paper sources

### NATIONAL: SENATE SHOULD CONSIDER SCOTUS PICK

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, March 21, 2016 Contact: PATRICK MURRAY

### Descriptive Methods Ch. 6 and 7

Descriptive Methods Ch. 6 and 7 Purpose of Descriptive Research Purely descriptive research describes the characteristics or behaviors of a given population in a systematic and accurate fashion. Correlational

### Statewide Survey of Louisiana Likely Voters on David Duke

Statewide Survey of Louisiana Likely Voters on David Duke The University of New Orleans Survey Research Center (SRC) sponsored an automated interactive voice response (IVR) telephone survey of likely Louisiana

### Literature Review of Sample Design and Methods

Literature Review of Sample Design and Methods Generally, a researcher employs sampling strategies in order to generate statistics and generalize findings to a larger population. Sampling refers to the

### POLLING STANDARDS. The following standards were developed by a committee of editors and reporters and should be adhered to when using poll results.

! POLLING STANDARDS June, 2006 The following standards were developed by a committee of editors and reporters and should be adhered to when using poll results. OVERVIEW Reporting on polls is no different

### CONFIDENCE INTERVALS I

CONFIDENCE INTERVALS I ESTIMATION: the sample mean Gx is an estimate of the population mean µ point of sampling is to obtain estimates of population values Example: for 55 students in Section 105, 45 of

### Sample Size Issues for Conjoint Analysis

Chapter 7 Sample Size Issues for Conjoint Analysis I m about to conduct a conjoint analysis study. How large a sample size do I need? What will be the margin of error of my estimates if I use a sample

### NATIONAL: TRUMP WIDENS NATIONAL LEAD

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, December 14, 2015 Contact: PATRICK

### NUMBERS, FACTS AND TRENDS SHAPING THE WORLD FOR RELEASE DECEMBER 30, 2013

NUMBERS, FACTS AND TRENDS SHAPING THE WORLD FOR RELEASE DECEMBER 30, 2013 Maeve Duggan, Research Assistant Aaron Smith, Senior Researcher 202.419.4500 RECOMMENDED CITATION: Maeve Duggan and Aaron Smith,

### Sampling in Marketing Research

Sampling in Marketing Research 1 Basics of sampling I A sample is a part of a whole to show what the rest is like. Sampling helps to determine the corresponding value of the population and plays a vital

### NATIONAL: ROMNEY EDGES OBAMA IN MONMOUTH POLL

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Released: Thursday, October 11, 2012 Contact: PATRICK MURRAY 732-263-5858 (office) 732-979-6769

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, August 3, Contact: PATRICK MURRAY 732-979-6769

### NEW HAMPSHIRE: TRUMP LEADS, BUSH SECOND

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Tuesday, July 28, 2015 Contact: PATRICK MURRAY

### NUMBERS, FACTS AND TRENDS SHAPING THE WORLD FOR RELEASE NOVEMBER 3, 2014 FOR FURTHER INFORMATION ON THIS REPORT: Aaron Smith, Senior Researcher

NUMBERS, FACTS AND TRENDS SHAPING THE WORLD FOR RELEASE NOVEMBER 3, 2014 FOR FURTHER INFORMATION ON THIS REPORT: Aaron Smith, Senior Researcher 202.419.4372 RECOMMENDED CITATION: Pew Research Center, November,

### IOWA: TRUMP TAKES CAUCUS LEAD

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Wednesday, 27, Contact: PATRICK MURRAY 732-979-6769

### Determining Sample Size 1

Fact Sheet PEOD-6 November 1992 Determining Sample Size 1 Glenn D. Israel 2 Perhaps the most frequently asked question concerning sampling is, "What size sample do I need?" The answer to this question

### TYPES OF SAMPLING. 2. Types of Non-probability Sample: There are the following four types of nonprobability PROBABILITY SAMPLING

TYPES OF SAMPLING 1. Types or Techniques Probability Sampling: There are a number of techniques of taking Probability sample. But here only six important techniques have been discussed as follows: 1. Simple

### Chapter 8: Quantitative Sampling

Chapter 8: Quantitative Sampling I. Introduction to Sampling a. The primary goal of sampling is to get a representative sample, or a small collection of units or cases from a much larger collection or

### Appendix I: Methodology

Appendix I: Methodology SSRS METHODOLOGY SSRS conducted a survey of Muslims and Jews for the Institute for Social Policy and Understanding from January 18 through January 27, 2016. The study investigated

### Constructing and Interpreting Confidence Intervals

Constructing and Interpreting Confidence Intervals Confidence Intervals In this power point, you will learn: Why confidence intervals are important in evaluation research How to interpret a confidence

### Introduction... 3. Qualitative Data Collection Methods... 7 In depth interviews... 7 Observation methods... 8 Document review... 8 Focus groups...

1 Table of Contents Introduction... 3 Quantitative Data Collection Methods... 4 Interviews... 4 Telephone interviews... 5 Face to face interviews... 5 Computer Assisted Personal Interviewing (CAPI)...

### Experimental data and survey data

Experimental data and survey data An experiment involves the collection of measurements or observations about populations that are treated or controlled by the experimenter. A survey is an examination

### Survey Sampling. Know How No 9 guidance for research and evaluation in Fife. What this is about? Who is it for? What do you need to know?

guidance for research and evaluation in Fife What this is about? Sampling allows you to draw conclusions about a particular population by examining a part of it. When carrying out a survey, it is not usually

### Public Support for Raising the Minimum Wage

Public for Raising the Minimum Wage Findings from a Survey of 805 Likely 2012 General Election Voters Nationwide Celinda Lake, Daniel Gotoff, and Alex Dunn Washington, DC Berkeley, CA New York, NY LakeResearch.com

### SAMPLING METHODS. Chapter 5

SAMPLING METHODS Chapter 5 1 LEARNING OBJECTIVES Reasons for sampling Different sampling methods Probability & non probability sampling Advantages & disadvantages of each sampling method 2 SAMPLING A sample

### Group Unweighted N Plus or minus Total sample 5,113 2.0 percentage points

METHODOLOGY The NBC News Online Survey was conducted online by SurveyMonkey September 16-8, 2015 among a national sample of 5,113 adults aged 18 and over. Respondents for this non-probability survey were

### Introduction to the Practice of Statistics Fifth Edition Moore, McCabe Section 8.1 Homework Answers

Introduction to the Practice of Statistics Fifth Edition Moore, McCabe Section 8.1 Homework Answers 8.1 In each of the following circumstances state whether you would use the large sample confidence interval,

### Is North Carolina a Red or Blue State? Politics and Men s College Basketball

Is North Carolina a Red or Blue State? Politics and Men s College Basketball Elon University Poll October 21-26, 2012 Kenneth E. Fernandez, Ph.D. Director of the Elon University Poll Assistant Professor

### SAMPLING DISTRIBUTIONS

0009T_c07_308-352.qd 06/03/03 20:44 Page 308 7Chapter SAMPLING DISTRIBUTIONS 7.1 Population and Sampling Distributions 7.2 Sampling and Nonsampling Errors 7.3 Mean and Standard Deviation of 7.4 Shape of

### Math 140: Introductory Statistics Instructor: Julio C. Herrera Exam 3 January 30, 2015

Name: Exam Score: Instructions: This exam covers the material from chapter 7 through 9. Please read each question carefully before you attempt to solve it. Remember that you have to show all of your work

### SAMPLING SIZE DETERMINATION IN FARMER SURVEYS. ICRAF Research Support Unit. Technical Note 4. Ric Coe Version January 1996

ICRAF Research Support Unit Technical Note 4 SAMPLING SIZE DETERMINATION IN FARMER SURVEYS Ric Coe Version January 1996 ICRAF World Agroforestry Centre PO Box 30677, Nairobi, Kenya Telephone : +54 54 000

### THE 2014 LATINO VOTE IN FLORIDA. October 9, 2014

THE 2014 LATINO VOTE IN FLORIDA October 9, 2014 Importance of Latino Voters in Florida Very tight race between incumbent Governor Scott and Former Governor Crist 1.6 million Latino registered voters Latinos

### Muhlenberg College/Morning Call 2016 Pennsylvania Republican Presidential Primary Survey. Early April

Muhlenberg College/Morning Call 2016 Pennsylvania Republican Presidential Primary Survey Key Findings: Early April 1. Donald Trump holds a modest lead over both Senator Ted Cruz and Ohio Governor John

### IOWA: CRUZ TAKES CAUCUS LEAD

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Monday, 7, Contact: PATRICK MURRAY 732-979-6769

### Marist College Institute for Public Opinion Poughkeepsie, NY 12601 Phone 845.575.5050 Fax 845.575.5111 www.maristpoll.marist.edu

Marist College Institute for Public Opinion Poughkeepsie, NY 12601 Phone 845.575.5050 Fax 845.575.5111 www.maristpoll.marist.edu POLL MUST BE SOURCED: NBC News/Marist Poll* Kansas: Orman Leads Roberts

### Study Procedures. Appendix A DEVELOPMENT QUESTIONNAIRE SAMPLED POPULATIONS

Appendixes Appendix A Study Procedures QUESTIONNAIRE A survey questionnaire was developed by the contractor- in-concert with OTA according to the detailed research objectives set forth by OTA. OTA staff,

### indicate how accurate the is and how we are that the result is correct. We use intervals for this purpose.

Sect. 6.1: Confidence Intervals Statistical Confidence When we calculate an, say, of the population parameter, we want to indicate how accurate the is and how we are that the result is correct. We use

### The Presidential Election, Same-Sex Marriage, and the Economy May 11-13, 2012

CBS NEWS/NEW YORK TIMES POLL For release: Monday, May 14th, 2012 6:30 pm (ET) The Presidential Election, Same-Sex Marriage, and the Economy May 11-13, 2012 The race for president remains close, but Republican

### TOTAL HAVE EVER DONE THIS DID YESTERDAY. Does anyone in your household have a Facebook account, or not?

Survey Questions WEB1-A Please tell me if you ever use the internet to do any of the following things. Do you ever use the internet to...[insert ITEM; RANDOMIZE; ALWAYS ASK ABOUT FACEBOOK LAST]? Based

### 65% of online adults use social networking sites

65% of online adults use social networking sites Women maintain their foothold on SNS use and older Americans are still coming aboard Mary Madden, Senior Research Specialist Kathryn Zickuhr, Research Specialist

### 4. Introduction to Statistics

Statistics for Engineers 4-1 4. Introduction to Statistics Descriptive Statistics Types of data A variate or random variable is a quantity or attribute whose value may vary from one unit of investigation

### THE TEA PARTY MOVEMENT: WHO THEY ARE April 5-12, 2010

CBS NEWS/NEW YORK TIMES POLL For release: Wednesday, April 14, 2010 6:30 pm (EDT) THE TEA PARTY MOVEMENT: WHO THEY ARE April 5-12, 2010 18% of Americans say they are supporters of the, but many have yet

### MAINE CONGRESSIONAL DISTRICT #2: MICHAUD LEADS HAMEL BY 21 PTS

MAINE CONGRESSIONAL DISTRICT #2: MICHAUD LEADS HAMEL BY 21 PTS FIRST-TERM CONGRESSMAN WELL POSITIONED IN RE-ELECTION BATTLE IN AN ELECTION TODAY FOR U.S. HOUSE OF REPRESENTATIVES IN MAINE'S 2ND CONGRESSIONAL

### BREAD AND BUTTER AND POLITICS: THE ECONOMY AND THE FALL CAMPAIGN March 28 th April 2 nd, 2008

CBS NEWS/NEW YORK TIMES POLL For Release: Thursday, April 3 rd, 2008 6:30 PM (EDT) BREAD AND BUTTER AND POLITICS: THE ECONOMY AND THE FALL CAMPAIGN March 28 th April 2 nd, 2008 The Democratic nomination

### Basic Principles of Survey Design. Thomas Lindsay Andrew Sell

Basic Principles of Survey Design Thomas Lindsay Andrew Sell Introductions Name, Institution, why are you here? Survey Review 5 minutes Political Participation and Attitudes Survey What is the research

### CHAPTER 15 NOMINAL MEASURES OF CORRELATION: PHI, THE CONTINGENCY COEFFICIENT, AND CRAMER'S V

CHAPTER 15 NOMINAL MEASURES OF CORRELATION: PHI, THE CONTINGENCY COEFFICIENT, AND CRAMER'S V Chapters 13 and 14 introduced and explained the use of a set of statistical tools that researchers use to measure

### NEW JERSEY VOTERS DIVIDED OVER SAME-SEX MARRIAGE. A Rutgers-Eagleton Poll on same-sex marriage, conducted in June 2006, found the state s

- Eagleton Poll Oct. 25, 2006 CONTACTS: MURRAY EDELMAN, Ph.D., (917) 968-1299 (cell) TIM VERCELLOTTI, Ph.D., (732) 932-9384, EXT. 285; (919) 812-3452 (cell) (Note: News media covering the New Jersey Supreme

### 101. Regardless of which candidate you happen to support, who do you think did the best job in the debate Hillary Clinton or Donald Trump?

Interviews with 521 registered voters who watched the presidential debate conducted by telephone (landline and cell) by ORC International on September 26, 2016. The margin of sampling error for results

### Sampling & Confidence Intervals

Sampling & Confidence Intervals Mark Lunt Arthritis Research UK Centre for Excellence in Epidemiology University of Manchester 18/10/2016 Principles of Sampling Often, it is not practical to measure every

### Marist College Institute for Public Opinion Poughkeepsie, NY 12601 Phone 845.575.5050 Fax 845.575.5111 www.maristpoll.marist.edu

Marist College Institute for Public Opinion Poughkeepsie, NY 12601 Phone 845.575.5050 Fax 845.575.5111 www.maristpoll.marist.edu NBC News/Marist Poll Nearly Seven in Ten New Jersey Voters Applaud Christie

### NEW HAMPSHIRE: TRUMP, SANDERS HOLD LEADS

Please attribute this information to: Monmouth University Poll West Long Branch, NJ 07764 www.monmouth.edu/polling Follow on Twitter: @MonmouthPoll Released: Sunday, 7, Contact: PATRICK MURRAY 732-979-6769

### Data network for better European organic market information SAMPLING. and its relevance for sound data collection

Data network for better European organic market information SAMPLING and its relevance for sound data collection OrganicDataNetwork Workshop, Bari, July 10 & 11, 2014 Corinna Feldmann, University of Kassel

### Confidence Intervals in Excel

Confidence Intervals in Excel By Mark Harmon Copyright 2011 Mark Harmon No part of this publication may be reproduced or distributed without the express permission of the author. mark@excelmasterseries.com

### Data Collection and Sampling OPRE 6301

Data Collection and Sampling OPRE 6301 Recall... Statistics is a tool for converting data into information: Statistics Data Information But where then does data come from? How is it gathered? How do we

### Auditing and Attestation Exam Review. Audit Sampling. Chapter Seven. Black CPA Review Chapter 7

Audit Sampling Chapter Seven Black CPA Review www.blackcpareview.com Chapter 7 Objectives: Objective 1: Understand sampling basics Objective 2: Understand sampling risk Objective 3: Understand attribute

### SURVEY OF PENNSYLVANIANS ON THE 2004 PRESIDENTIAL ELECTION

The Morning Call/ Muhlenberg College Institute of Public Opinion SURVEY OF PENNSYLVANIANS ON THE 2004 PRESIDENTIAL ELECTION KEY FINDINGS REPORT October 22, 2004 KEY FINDINGS: 1. The race for Pennsylvanian

### CONFIDENCE INTERVALS FOR MEANS AND PROPORTIONS

LESSON SEVEN CONFIDENCE INTERVALS FOR MEANS AND PROPORTIONS An interval estimate for μ of the form a margin of error would provide the user with a measure of the uncertainty associated with the point estimate.