Picturing repeated measures: Comments on Loftus, Morrison, and others

Abstract

Loftus’s (1993b, 1995) recommendation that investigators routinely include plots of appropriate means along with 95% confidence intervals or some other indication of variability has considerable merit, yet we agree with Morrison and Weaver (1995) that such plots can supplement but not supplant the usual reporting of analysis of variance results. Providing them may be easier than Loftus and Masson (1994) indicated, especially when error bars are understood as supplemental descriptive devices. We suggest a general, unified approach that applies to the explication of both between- and within-subjects effects. Variability is estimated separately for each group of scores identified as different by analysis because this serves description better. Raw scores are used for between-subjects effects, scores adjusted for between-subjects variability for within-subjects effects. All computations and figures are easily effected using common spreadsheet programs.

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References

  1. Bakeman, R. (1992).Understanding social science statistics: A spreadsheet approach. Hillsdale, NJ: Erlbaum.

    Google Scholar 

  2. Cohen, J. (1968). Multiple regression as a general data-analytic system.Psychological Bulletin,70, 426–443.

    Article  Google Scholar 

  3. Cohen, J. (1990). Things I have learned (so far).American Psychologist,45, 1304–1312.

    Article  Google Scholar 

  4. Cohen, J., &Cohen, P. (1983).Applied multiple regression/correlation analysis for the behavioral sciences. Hillsdale, NJ: Erlbaum.

    Google Scholar 

  5. Edgington, E. S. (1987).Randomization tests. New York: Marcel Dekker.

    Google Scholar 

  6. Fisher, R. A. (1970).Statistical methods for research workers (14th ed.). Edinburgh: Oliver & Boyd. (Original work published 1925)

    Google Scholar 

  7. Good, P. (1994).Permutation tests: A practical guide to resampling methods for testing hypotheses. New York: Springer-Verlag.

    Google Scholar 

  8. Greenhouse, S. W., &Geisser, S. (1959). On methods in the analysis of profile data.Psychometrika,24, 95–112.

    Article  Google Scholar 

  9. Hays, W. L. (1963).Statistics. New York: Holt, Rinehart & Winston.

    Google Scholar 

  10. Hochberg, Y., &Tamhane, A. C. (1987).Multiple comparison procedures. New York: Wiley.

    Google Scholar 

  11. Keppel, G. (1991).Design and analysis: A researcher’s handbook (3rd ed.). Englewood Cliffs, NJ: Prentice-Hall.

    Google Scholar 

  12. Kirk, R. E. (1982).Experimental design: Procedures for the behavioral sciences (2nd ed.). Belmont, CA: Brooks/Cole.

    Google Scholar 

  13. Loftus, G. R. (1991). On the tyranny of hypothesis testing in the social sciences.Contemporary Psychology,36, 102–105.

    Article  Google Scholar 

  14. Loftus, G. R. (1993a). Editorial comment.Memory & Cognition,21, 1–3.

    Article  Google Scholar 

  15. Loftus, G. R. (1993b). A picture is worth a thousandp values: On the irrelevance of hypothesis testing in the microcomputer age.Behavior Research Methods, Instruments, & Computers,25, 250–256.

    Article  Google Scholar 

  16. Loftus, G. R. (1995). Data analysis as insight: Reply to Morrison and Weaver.Behavior Research Methods, Instruments, & Computers,27, 57–59.

    Article  Google Scholar 

  17. Loftus, G. R., &Masson, M. E. J. (1994). Using confidence intervals in within-subject designs.Psychonomic Bulletin & Review,1, 476–490.

    Article  Google Scholar 

  18. Morrison, G. R., &Weaver, B. (1995). Exactly how manyp values is a picture worth? A commentary on Loftus’s plot-plus-error-bar approach.Behavior Research Methods, Instruments, & Computers,27, 52–56.

    Article  Google Scholar 

  19. Rosnow, R. L., &Rosenthal, R. (1989). Statistical procedures and the justification of knowledge in psychological science.American Psychologist,44, 1276–1284.

    Article  Google Scholar 

  20. Tukey, J. W. (1977).Exploratory data analysis. Reading, MA: Addison-Wesley.

    Google Scholar 

  21. Turkheimer, M., Bakeman, R., &Adamson, L. B. (1989). Do mothers support and peers inhibit skilled object play in infancy?Infant Behavior & Development,12, 37–44.

    Article  Google Scholar 

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Correspondence to Roger Bakeman.

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We would like to thank C. Chin and C. Davis, graduate students at Georgia State University, whose questions in class first caused us to consider these issues more closely, and D. Borkman Reed for her helpful editorial comments.

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Bakeman, R., Mcarthur, D. Picturing repeated measures: Comments on Loftus, Morrison, and others. Behavior Research Methods, Instruments, & Computers 28, 584–589 (1996). https://doi.org/10.3758/BF03200546

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Keywords

  • Separate Estimate
  • Adjusted Score
  • Pool Error Term
  • Separate Formula
  • Timated Standard Error