The telephone company surveys its customers to see how many

The telephone company surveys its customers to see how many would like even more expanded services, like call forwarding to your cell phone, linked voice mail systems, etc. Out of 240 customers surveyed, 139 of them were in favor of expanded service. The company president will implement this plan if there is over 50% in favor of expanded service. What is the test statistic for this hypothesis test?

Solution

The test statistic is

Z=(phat-p)/sqrt(p*(1-p)/n)

=(139/240-0.5)/sqrt(0.5*0.5/240)

=2.45