It is desired to estimate the time it takes Statistics I students to finish a computer project to within 2 hours at 95% reliability. It is estimated that the standard deviation of the times is 14 hours. How large a sample should be taken to get the desired interval? Hint: Think about margin of error.

Solution: The 95% margin of error is equal to

We need to be within 2 hours, which means that

which means that the sample size should be at least 189.