1 / 15

Chapter 8

Chapter 8. Making Sense of Statistical Significance: Effect Size, Decision Errors, and Statistical Power. Effect Size. Amount that two populations do not overlap Figuring effect size ( d ) Effect size conventions small d = .2 medium d = .5 large d = .8. Meta-Analysis.

colman
Download Presentation

Chapter 8

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 8 Making Sense of Statistical Significance: Effect Size, Decision Errors, and Statistical Power

  2. Effect Size • Amount that two populations do not overlap • Figuring effect size (d) • Effect size conventions • small d = .2 • medium d = .5 • large d = .8

  3. Meta-Analysis • Combines results from different studies • Provides an overall effect size • Common in the more applied areas of psychology

  4. Decision Errors • Type I error • Reject the null hypothesis when in fact it is true • alpha (α) • Probability of making a Type I error • Type II error • Not rejecting the null hypothesis when in reality it is false • beta (β) • Probability of making a Type II error

  5. Possible Correct and Incorrect Decisions in Hypothesis Testing

  6. Statistical Power • Probability that the study will produce a statistically significant results if the research hypothesis is true

  7. Statistical Power • Steps for figuring power 1. Gather the needed information: mean and standard deviation of Population 2 and the predicted mean of Population 1 2. Figure the raw-score cutoff point on the comparison distribution to reject the null hypothesis

  8. Statistical Power • Steps for figuring power 3. Figure the Z score for this same point, but on the distribution of means for Population 1 4. Use the normal curve table to figure the probability of getting a score more extreme than that Z score

  9. Influences on Power • Effect size • Difference between the population means • Population standard deviation • Figuring power from predicted effect sizes

  10. Influences on Power • Sample size • Affects the standard deviation of the distribution of means • Significance level (alpha) • One- versus two-tailed tests • Type of hypothesis-testing procedure

  11. Summary of Influences on Power

  12. Practical Ways of Increasing the Power of a Planned Study

  13. Importance of Power When Evaluating Study Results • When a result is significant • Statistical significance versus practical significance • When a result if not statistically significant

  14. Controversies and Limitations • Effect size versus statistical significance • Theoretically oriented psychologists emphasize significance • Applied researchers emphasize effect size

  15. Reporting in Research Articles • Increasingly common for effect sizes to be reported • Commonly reported in meta-analyses

More Related