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Meta-analysis

Meta-analysis. Overview. Overview. Definition A meta-analysis statistically combines the results of several studies that address your intended research hypothesis. A study collects data from individual subjects (such as 100 subjects = 100 “data points”)

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Meta-analysis

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  1. Meta-analysis Overview

  2. Overview • Definition • A meta-analysis statistically combines the results of several studies that address your intended research hypothesis. • A study collects data from individual subjects (such as 100 subjects = 100 “data points”) • A meta-analysis collects data from individual studies (such as 100 studies = 100 “data points”)

  3. Steps 1. Define your hypothesis 2. Locate studies 3. Find “effect size” for each study 4. Average the “effect sizes” together 5. If you want, you can analyze “moderators” 6. Write the manuscript

  4. Step1 • Define your hypothesis • e.g., Does “authoritarianism” predict verdict choice? relationship between X and Y relationship between authoritarianism and verdict

  5. Step 2 • Locate studies • e.g., Sannito & Arnolds (1982) McGowen & King (1982) Boehm (1968) etc.

  6. Step 3 • Find “effect size” for each study • e.g., convert data (means, p-value, etc) to “r” or “d” in Boehm (1968) effect of X on Y was .21 in McGowen & King (1982) the effect was .11 etc.

  7. Step 4 • Average the “effect sizes” together • e.g., weight by sample size, then take mean so total effect of X on Y across studies was .17 so authoritarianism attitude does predicts verdicts

  8. Step 5 • If you want, you can analyze “moderators” • e.g., does the “average effect size” get smaller or bigger based upon factors like if the studies have actual jurors versus college students, or if the studies employ written summaries versus actual trials, etc.

  9. Why do a meta-analysis? • Easy • Steps are simple, there is software to calculate most things • Cost-effective • Since you have already read a bunch of articles to write a paper, not much more work to synthesize them together • Can publish if don’t have access to Ss or Subject Pools • Best type of article • Most highly cited type of article. • Advantages of both qualitative and quantitative research • Truly answers research questions within the literature (compared to single studies which can’t truly generalize)

  10. We will be using… • PsychWiki http://psychwiki.com/wiki/Stenstrom_Lab_Group (click on SLG – Meta-analysis) • My “Quals” as an example (I’ll email it to you)

  11. Some cool things about meta-analyses…

  12. Some cool things about meta-analyses… • ES - Publishable no matter what the result of the average effect size because descriptive • Significance – Non significant results are still publishable because descriptive • Ss - Does not rely upon unpredictable human subjects to collect data so you have more control • Moderators – The meta analysis can be starting place for line of research testing significant moderators

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