Survey research and design in psychology/Lectures/Power & effect sizes

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Lecture 09: Power & effect sizes

Resource type: this resource contains a lecture or lecture notes.

This is the ninth lecture for the Survey research and design in psychology unit of study.

Outline

Explains use of, and issues involved in,

1. significance testing
2. inferential decision making
3. statistical power
4. effect sizes
5. confidence intervals
6. publication bias
7. academic integrity

The lecture resources include presentation slides, audio and video recordings, and additional notes.

Conclusions

• Decide on H₀ and H₁ (1 or 2 tailed)
• Calculate power beforehand and adjust the design to detect a minimum effect size (ES)
• Report statistical power, statistical significance, ES, confidence interval
• Compare results with meta-analyses and/or meaningful benchmarks
• Take a balanced, critical approach, striving for objectivity and academic integrity

Readings

1. Howitt and Cramer (2011a):
   1. Chapter 34: The size of effects in statistical analysis: Do my findings matter? (pp. 419-425)
   2. Chapter 35: Meta-analysis: Combining and exploring statistical findings from previous research (pp. 426-441)
   3. Chapter 37: Confidence intervals (pp. 455-464)
   4. Chapter 39: Statistical power: Getting the sample size right (pp. 486-507)
2. Howitt and Cramer (2014a):
   1. Chapter 35: The size of effects in statistical analysis: Do my findings matter? (pp. 487-494)
   2. Chapter 36: Meta-analysis: Combining and exploring statistical findings from previous research (pp. 495-514)
   3. Chapter 38: Confidence intervals (pp. 529-539)
   4. Chapter 40: Statistical power: Getting the sample size right (pp. 562-586)
3. Wilkinson, L., & APA Task Force on Statistical Inference. (1999). Statistical methods in psychology journals: Guidelines and explanations. American Psychologist, 54, 594-604.

Handout

• 2015 handouts:
  • Download 6 slides to a page:
  • Download 3 slides to a page:

See also

• Multiple linear regression II (Previous lecture)
• Summary & conclusion (Next lecture)
• Funnel plot (Wikipedia)

External links

• Lecture slides (slideshare)
• p values and statistical significance (A New View of Statistics]
• Statistical power analysis quiz (Practice) (Howitt & Cramer, 2011)