Question

Historically, evening long-distance calls phone calls from a particular city have averages 12 minutes per call. In a random sample of 20 calls, the sample mean was 10.7 minutes per call with a standard deviation of 4 minutes. Does the sample indicate a change in the mean duration of long distance calls? Test the hypothesis at 10% level of significance, state the hypothesis and report your conclusion.

a. estimate the p-value and show your work.

Answer 1

Solution :

= 12

=10

s =4

n = 20

This is the two tailed test .

The null and alternative hypothesis is ,

H0 :    = 12

Ha :     12

Test statistic = t

= ( - ) / s / n

= (10-12) / 4 / 20

= −2.236

Test statistic = t = −2.236

P-value =0.0375

= 0.10  

P-value <

0.0375 < 0.10

Reject the null hypothesis .

There is sufficient evidence to suggest that