Question

Suppose that, as course instructor, you decide instead that you want to calculate a 95% confidence interval for the population proportion of all Cal Poly students who have ever marched in a Memorial Day Parade, and that you would like the margin of error of your 95% confidence interval to be .05, and that you would like to use a (most) conservative sample size for this task. What sample size should you use

Answer 1

Answer: 385

Explanation:

If prior population proportion p is unknown, then the formula to compute sample size will be:

`n= 0.25((z^*)/(E))^2`

where, E= Margin of error, z* = Critical zvalue

Given: E= 0.05

Critical value for 95% confidence = 1.96

Required sample size:
`n=0.25((1.96)/(0.05))^2`

`\\=384.16\approx385`

Hence, the required sample size = 385