Exercise

# Sample size and treatment difference

The clinician is unsure of the expected treatment difference but believes it would be between 0.5 and 2.0. Using 80% power and standard deviation of 3, provide them with a set of sample sizes required for this range of differences as a table and in a plot.

The `ggplot2`

library has been loaded for this session.

Instructions

**100 XP**

- Generate a vector,
`delta`

, containing values between 0.5 and 2.0, incrementing by 0.25. - Use a
`for`

loop to generate the sample sizes for each of the treatment differences. - Put the treatment differences and resulting sample sizes in a data frame.
- Use
`ggplot()`

to display the treatment differences and sample sizes.