28.4 Group variance if only 10 or 20 can be tested

p <- power.anova.test(groups = 3,
                 between.var = NULL,
                 within.var = mean(sds*sds),
                 sig.level = .05, power = 0.8,
                 n = 10)
p

## 
##      Balanced one-way analysis of variance power calculation 
## 
##          groups = 3
##               n = 10
##     between.var = 653
##      within.var = 1210
##       sig.level = 0.05
##           power = 0.8
## 
## NOTE: n is number in each group

Note this is a σ of the group means of 18.07

p <- power.anova.test(groups = 3,
                 between.var = NULL,
                 within.var = mean(sds*sds),
                 sig.level = .05, power = 0.8,
                 n = 20)
p

## 
##      Balanced one-way analysis of variance power calculation 
## 
##          groups = 3
##               n = 20
##     between.var = 307
##      within.var = 1210
##       sig.level = 0.05
##           power = 0.8
## 
## NOTE: n is number in each group

Note this is a σ of the group means of 12.4