# pwr.anova.test : increasing power, decreases sample size?

I am trying to calculate how many samples I need for an ANOVA with 2 groups, effect size of 0.3, significance of 0.05 and power of 0.8.

'''pwr.anova.test(k=2, f=.4, sig.level =.05, power =.8)

Balanced one-way analysis of variance power calculation

          k = 2
n = 44.58577
f = 0.3
sig.level = 0.05
power = 0.8


NOTE: n is number in each group.'''

I tried different effect sizes and when I increase the effect size, 'n' decreases, whereas I would expect that more samples would be required to achieve a greater effect size? I'm confused...am I missing something here?

• When the effect size is huge, how many samples do you really need to see it??
– whuber
Mar 4, 2020 at 17:01