Confidence interval

Question

study of the ages of motorcyclists killed in crashes involves the random selection of 139

drivers with a mean of 35.31 years. Assuming that σ=10.1 ​years, construct and interpret a 99​% confidence interval estimate of the mean age of all motorcyclists killed in crashes

What is the 99% confidence interval for the population mean?

Answer 1

The mean age is 35.31 years with a std of 10.1 years. z_alpha/2 for a 99% CI is 2.576. n=139.

The formula for the CI is

mean -/+ z_alpha/2*std/sqrt(n)

Plug in the numeric values and solve to get

35.31 -/+ 2.576*10.1/sqrt(139)

35.31 -/+ 2.21 which is

(33.10, 37.52)