Power analysis — one-way ANOVA
Sample size or power for a one-way ANOVA with effect size f (.10 small, .25 medium, .40 large).
Menu: Analyze → Power Analysis → One-Way ANOVA…
When should I use it?
- Planning a study with three or more groups.
What are the assumptions?
- Equal group sizes (the total N is a multiple of the number of groups).
How do I run it in StatLab?
- Give f, the number of groups, α and the target power (or the total N).
How do I read the output?
| Output | Meaning |
|---|---|
| Noncentrality λ | f² × N. |
| Total sample size / Actual power | Result of the search. |
Worked example
On the practice survey dataset (File → Sample dataset), this command — which the dialog's Paste button also produces — runs the procedure:
PROC pwAnova /mode=n /f=0.25 /groups=3 /alpha=0.05 /power=0.8.
Output tables: Power — ANOVA: fixed effects, omnibus, one-way (a priori).
How would I report it in APA style?
A sample of 159 gives power .805 to detect the stated effect at α = .050.
Computed by StatLab's validated procedure code when this page was built. The example only illustrates the steps; choose variables that fit your own research question.
What are common mistakes?
- Confusing f with eta-squared (f² = η² / (1 − η²)).