A researcher is interested in estimating the average salary of teachers in a large urban school district. She wants to be 95% confident that her estimate is correct. If the standard deviation is $1050 (σ = 1050), how large of a sample is needed to be accurate within $200 (E = 200)? That is, find n.

Answer 1

Formula:

n = [(z-value * sd)/E]^2
...where n = sample size, z-value will be 1.96 using a z-table to represent the 95% confidence interval, sd = 1050, E = 200, ^2 means squared, and * means to multiply.

Plug the values into the formula and calculate the sample size. Round your answer to the next highest whole number.

I hope this will help get you started.

Answer 2

105.88

Answer 3

n= 106