I'm trying to find which type of statistical test I need for the study below (inputting into SPSS). I was thinking it could be repeated measures ANOVA or numerous paired t-tests??? Thoughts please...

Title: A study into the effects of acute creatine supplement on cognitive function of sleep deprived subjects.

  • 1 Group (n=11)
  • 4 weeks of testing
  • 3 cognition tests
  • 2 supplements: Creatine & Placebo
  • 2 conditions: Sleep deprived and non-sleep deprived

  • Week 1: Non-sleep deprived & Creatine (3 cognitive tests)

  • Week 2: Non-sleep deprived & Placebo (3 cognitive tests)
  • Week 3: Sleep deprived & Creatine (3 cognitive tests)
  • Week 4: Sleep deprived & Placebo (3 cognitive tests)
  • $\begingroup$ Were there any time lapses between weeks? Or are the 4 weeks consecutive? $\endgroup$ – Penguin_Knight Feb 27 '14 at 16:33
  • $\begingroup$ @Penguin_Knight the 4 tests were done over 2 months, and it wasn't necessary for certain time lapses between the weeks (no effecting dominators) $\endgroup$ – Harry Feb 27 '14 at 16:41

A within-subjects ANOVA is preferred over paired t-tests both because it protects against family-wise alpha inflation and allows you to analyze the potential interactive effects of your two factors.

However ,your sample size is also quite small. I would look carefully to ensure that the ANOVA assumptions are met. If not, you might consider a Friedman Test.

T-tests (parametric) or Wilcoxon signed-rank tests (non-parametric) would have to follow a significant omnibus test to determine precisely where the differences lie.


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