### Question Description

You are designing a study to be evaluated with a two-sample
nondirectional independent *t* test at *a* = .05.
You want .90 power. You expect
Cohen’s *d *to be about .40. How many subjects will you need peer group?

## Explanation & Answer

Thank you for the opportunity to help you with your question!

j=d*sqrt(n/2)

where j is the power of the test

d is the cohen's d

n is the sample size per group

0.9=0.4 sqrt(n/2)

0.81=0.16n/2

1.62=0.16n

n=10

the number of subjects is 10 per sample