In the department store example, imagine that the sample had been N = 4 rather than N = 25 (for the sake of this example, keep the sample mean and standard deviation at 18.50 and 2.25, respectively).

a. State the null and alternative hypotheses (H₀ and H₁) (allow for the possibility that the average age may be younger than 16).

IV: Cellular phone use; DV: Number of traffic accidents

b. Example: Determine the number of traffic accidents each person has experienced in the past year.

c. Example of experimental: Use a driving simulation with the “driver” talking on a phone and measure the number of potential driving mistakes or accidents.
Example of nonexperimental: Take a survey of the number of accidents people have been in and whether or not they were using a phone during the accident.

b. Make a decision about the null hypothesis.
(1) Calculate the degrees of freedom (df ).
(2) Set alpha (α), identify the critical values, and state a decision rule. Why is the decision rule different than when N = 25?
(3) Calculate a statistic: t-test for one mean. Why is it a different value than when N = 25?
(4) Make a decision whether to reject the null hypothesis.
(5) Determine the level of significance.

c. Draw a conclusion from the analysis.

d. What are the implications of this analysis for the store manager’s claim?