Question

Write the null and alternative hypotheses for each of the following examples. Determine if each is a case of a two-tailed, a left-tailed, or a right-tailed test. Also determine the sampling distribution for the hypothesis test.

a.To test if the mean number of hours spent working per week by college students who hold jobs is different from 20 hours.

b.To test whether or not a bank’s ATM is out of service for an average of more than 10 hours per month.

c.To test if the mean length of experience of airport security guards is different from 3 years.

d.To test if the mean credit card debt of college seniors is less than $1000.

e.To test if the mean time a customer has to wait on the phone to speak to a representative of a mail-order company about unsatisfactory service is more than 12 minutes.

Answer 1

Solution:

a)

The null and alternative hypothesis are

H₀ : = 20 vs H_a :    20

Two tailed test

b)

The null and alternative hypothesis are

H₀ : 10 vs H_a : > 10

Right tailed test

c)

The null and alternative hypothesis are

H₀ : = 3 vs H_a :    3

Two tailed test

d)

The null and alternative hypothesis are

H₀ : 1000 vs H_a : < 1000

Left tailed test

e)

The null and alternative hypothesis are

H₀ :    12 vs H_a : > 12

Right tailed test