Question

You want to estimate the average gas price in your city for a gallon of regular gas. You take a random sample of prices from 15 gas stations​ , recording an average cost of ​$2.53 and a standard deviation of ​$0.12. Create a 99​% confidence interval for the mean price per gallon of gas. 

Answer 1

n= 15

s = 0.12

SE = s/

= 0.12/

= 0.0310

= 0.01

ndf = 15 - 1 = 14

From Table, critical values of t = 2.9768

Confidence Interval:

2.53 (2.9768 X 0.0310)

=2.53 0.0922

= ( 2.44,2.62)

Confidence Interval:

2.44 <   <   2.62