Question

1) Faculty members at a large university are irritated by students’ cell phones and complain that a cell phone rings in class on average more than 15 times per semester. A reporter at the school newspaper thinks that students are now more courteous. The reporter asks a random sample of 25 teachers to keep track of the number times a cell phone rings during the semester. The sample mean is 13.9 with a standard deviation is 2.7 calls. Test the faculty’s claim that mean number of times per semester that a cell phone rings in class is at least 15 at α = .05 significance level.

Answer 1

Solution:

This is a left (One) tailed test,

The null and alternative hypothesis is,  

Ho: 15

Ha: 15

The test statistics,

t =( - )/ (s /n)

= ( 13.9 - 15 ) / ( 2.7 / 25 )

= -2.037

P-value = 0.0264

The p-value is p = 0.0264 < 0.05, it is concluded that the null hypothesis is rejected.

There is sufficient evidence to claim that mean number of times per semester that a cell phone rings in class is at least 15 at α = .05 significance level.