Question

a) Identify the claim: state the null and alternative hypotheses. b) Determine the test: left-tailed, right-tailed, or two-tailed. c) Identify the degree of freedom and determine the critical value. d) Graph your bell-shaped curve and label the critical value. e) Find your standardized test statistic ? and label it on your graph. f) Decide whether to reject or fail to reject the null hypothesis. g) Interpret your result.

A dealership projected that the mean waiting time at a dealership is less 5 minutes. To check the claim, the dealership randomly selects 20 customers and gets a mean of 4.5 minutes with a standard deviation of 0.8 minutes. At α = 0.05, test the dealership’s claim.

Answer 1

Solution-A:

Ho:mu=5

Ha:mu<5

) Determine the test: left-tailed, right-tailed, or two-tailed.

since mean waiting time at a dealership is less 5 minutes,its a left tail t test

left tail

c) Identify the degree of freedom and determine the critical value.

degrees of freedom=n-1=20-1=19

alpha=0.05

t critical value in excel

=T.INV(0.05,19)

=-1.729132812

test statistic<critical t value

Reject Ho

if test statistic>critical t value

Fail to reject Ho

d) Graph your bell-shaped curve and label the critical value.