M.Higgins - Emory School of Nursing: Power Lectures and G*Power Exercises

PPT Slides

• Understanding “Power” - Type I and Type II Errors
• Learning how to compute power, sample size and effect sizes
• PPT SLIDES - click to download

Power Analysis Software

• G*Power (FREE)
  • https://www.psychologie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower
  • register, then scroll down to download software
  • more help at UCLA - Advanced Research Computing: Statistical Methods and Data Analytics, https://stats.oarc.ucla.edu/other/gpower/
• NCSS/PASS
  • This software does cost money, but the documentation is FREE to access and read.
  • Go to FREE Documentation at https://www.ncss.com/software/pass/pass-documentation/
  • Go to Introduction and Read “Intro to Power Analysis” at https://www.ncss.com/wp-content/themes/ncss/pdf/Procedures/PASS/Introduction_to_Power_Analysis.pdf

Converting Effect Sizes and Interpretation

A really helpful website:

• https://www.psychometrica.de/effect_size.html - go to item 14 to convert between different effect sizes
• https://www.psychometrica.de/effect_size.html - also see item 16 for “Table of interpretation for different effect sizes””

Some useful papers to read

• “Post hoc power analysis: an idea whose time has passed?” by M. Levine, M. H. Ensom https://pubmed-ncbi-nlm-nih-gov.proxy.library.emory.edu/11310512/
• “The Abuse of Power: The Pervasive Fallacy of Power Calculations for Data Analysis” John M. HOENIG and Dennis M. HEISEY https://www.vims.edu/people/hoenig_jm/pubs/hoenig2.pdf