posted by paula on .
a pizza shop owner wishes to find the 95% confidence interval of the true mean cost of a large plain pizza. how large should the sample be if she wishes to be accurate to within $0.15? a previous study showed that the standard deviation of the price was $0.26
Use a formula to find sample size.
Here is one:
n = [(z-value * sd)/E]^2
...where n = sample size, z-value = 1.96 for 95% confidence, sd = 0.26, E = 0.15, ^2 means squared, and * means to multiply.
Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.