Statisitics Question

Question

Assume that a sample is used to estimate a population mean . Find the 95% confidence interval for a sample of size 38 with a mean of 44.3 and a standard deviation of 5.1. Enter your answer accurate to one decimal place.I am 95% confident that the mean  is between___  and ____

Answer 1

The 95% confidence interval is:

sample mean +/- z(alpha/2) * standard deviation/sqrt(sample size)

You are given sample mean, standard deviation and sample size in problem statement.

To find z:

alpha/2 = (100-95)/2 = 0.025 (tail probabilities for upper and lower tail)

since normal table cumulative, look up z value corresponding to 0.975

You are given other data, so you can just plug into formula and compute answer.