What is secondary data?

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Vanessa Harmon
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1 The Advantages and Disadvantages of Introduction June, 2012 Definition What is secondary data? 2 Primary Data (What it is not) Primary data Data collected by a researcher (or group) Data collected for a specific purpose Example Research team conceives and develops a research project Team collects data specific to planned research question posed by the project Team performs analysis and publishes results of the data collected 3, UCD School of Public Health, Physiotherapy and Population Science

2 Data that is not primary data Reasons for secondary data Data collected by outside source Data collected for alternate objective Examples Government statistics Previous studies Secondary questions 4 What does secondary data look like? Can be large databases Can be actual data from outside study Can be descriptive statistics from a journal article Can be a collection across various sources 5 Use of Secondary data can Directly answer some research questions Trends Descriptions Associations Cause? Generate research questions Guide design of studies Secondary data is the starting place for most studies. 6, UCD School of Public Health, Physiotherapy and Population Science

3 Advantages of Cost Time Money Allows broader comparisons Across time Across political boundaries Collected by experts in data collection Allows for complicated sampling methods Can access hard to reach populations 7 Main Limitation Restricted by original study design Might not have sampled desired population Results only generalize to sampled population Might not have measured all traits of interest Might not have measured trait as desired age as categories instead of actual age define race as White or Other 8 Additional Limitation Doesn t answer why Tells what the situation is Wrist injuries common to hurlers Tells where the situation might occur Hurling common in Cork, Kilkenney, Tipperary and Dublin Doesn t tell us why hurling is associated with wrist injuries or why hurling is popular in those counties. 9, UCD School of Public Health, Physiotherapy and Population Science

4 Disadvantages Quality of data difficult to assess Sources may conflict In findings Or choice of measure Inclusion/exclusion criteria can cause bias Data reported as aggregates the more aggregated the data the more invisible the individuals 10 Locating Appropriate Many sources Government Academic Industry Collaborative research With so much available in the electronic age, how to find the right data? 11 Matching data and project Start with well defined research question Specify population of interest Specify variables to include in analysis Identify kind of data national survey hospital records transcripts of interviews Create list of available data sets Interactive process 12, UCD School of Public Health, Physiotherapy and Population Science

5 Considerations What data to use? What is the quality of the data? What was the original purpose? What, when and how was it collected? What cleaning procedures have been applied? 13 Tools for Analysis Database tools Access SQL Statistical packages SAS SPSS Analysis specific software RevMan for meta-analysis 14 Ethics? Informed consent? Anonymous data? Find balance Optimal use of data Protection of individuals 15, UCD School of Public Health, Physiotherapy and Population Science

An Introduction to Secondary Data Analysis

1 An Introduction to Secondary Data Analysis What Are Secondary Data? In the fields of epidemiology and public health, the distinction between primary and secondary data depends on the relationship between