Question

Listed below are the ages (years) of randomly selected race car drivers. Construct an 80% confidence interval estimate of the mean age of all race car drivers :

32, 32, 33, 33, 41, 29, 38, 32, 33, 23, 27, 45, 52, 29, 25

Answer 1

Confidence interval for Population mean is given as below:

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Xbar = 33.6

S = 7.669978581

n = 15

df = n – 1 = 14

Confidence level = 80%

Critical t value = 1.3450

(by using t-table)

Confidence interval = Xbar ± t*S/sqrt(n)

Confidence interval = 33.6 ± 1.3450*7.669978581/sqrt(15)

Confidence interval = 33.6 ± 2.6637

Lower limit = 33.6 - 2.6637 = 30.94

Upper limit = 33.6 + 2.6637 = 36.26

Confidence interval = (30.94, 36.26)