Schmidt & Hunter Approach to d

1. Schmidt & Hunter Approach to d

2. Statistical Artifacts • Extraneous factors that influence observed effect • Sampling error • Reliability-note applications to experiments • Range restriction-note effect on d • Computational error • Dichotomization of variables

3. Effect sizes d and rpb

4. ES d and rpb (2) N=6 Note rpbis computed as an ordinary Pearson correlation. Note SDY not SDpooled. If sample sizes are unequal, replace ‘2’ with ‘1/sqrt(pq)’.

5. Estimated Sampling Error Variance • The variance of d Estimated variance for a study. Bias adjustment

6. Bare-Bones Analysis (1) One approach is to convert d to r and analyze r. You can convert back to d at the end. Suppose you find that:

7. Bare-Bones (2) For bare-bones: For bare-bones, a simpler formula is used for the variance of error.

8. Example (1)

9. Example (2)

10. Example (3)

11. Example (4)

12. Example Psychometric M-A Sum Mean

13. Example (2)

14. Example (3)

15. k=4 dbaro=.28 M-A Summary