Exercise

# Sample size for unequal groups

Here we will calculate the sample size required for a trial where patients will be randomized to active treatment and placebo in a 2:1 ratio for a two-sided t-test. The `samplesize`

library has been loaded for this session.

Instructions

**100 XP**

- Use the
`n.ttest()`

function within the`samplesize`

package to calculate the sample size for a trial with an expected treatment difference of 1.5, common standard deviation of 2.5, 90% power, and a 2:1 ratio.