80 Power 90 Power Number of Groups Number of Groups Effect S

.80 Power                               .90 Power

Number of Groups                  Number of Groups

Effect Size               3            4              5                    3            4                   5

.100 ( small )           322          271          240                417        350               310

. 196                          80             68            60                106        88                  78

.243                          52            44            39                  68          58                   50

.287                          36             31            27                  48           40                35

.371 ( large )            21             18            16                   27          23                20

.447                         14              12            11                   18          15              13

.573                        8                 7              6                      10         9                8

Design a three group study to be evaluated with a one way ANOVA at =.05.

You expect effect size to be about .29. How many subjects will you need per group for .80 power?

Solution