Question

Noise levels at 5 airports were measured in decibels yielding the following data:

152,154,139,124,120

Construct the 80% confidence interval for the mean noise level at such locations. Assume the population is approximately normal.

Step 1 of 4 :  

Calculate the sample mean for the given sample data. Round your answer to one decimal place.

Answer 1

Solution :

= (152 + 154 + 139 + 124 + 120) / 5 = 689 / 5 = 137.8

s = 15.6

sample size = n = 5

Degrees of freedom = df = n - 1 = 4

t _/2,df = 1.533

Margin of error = E = t_/2,df * (s /n)

= 1.533 * (15.6 / 5)

Margin of error = E = 10.7

The 80% confidence interval estimate of the population mean is,

- E < < + E

137.8 - 10.7 < < 137.8 + 10.7

127.1 < < 148.5

(127.1 , 148.5)