2. (Page 390) Determine the critical value(s) of the test statistic for each of the following large sample tests for the comparison of two population means.

a. Left-tailed test, a =0.04

b. Right-tailed test, a =0.08

c. Two-tailed test, a =0.02

4. .(p.390) An internal auditor for Tiger Enterprises has been asked to determine if there is a difference in the average amount charged for daily expenses by two top salesmen, Mr. Ellis and Mr. Ford. The auditor randomly selects 45 days and determines the daily expenses for each of the salesmen.                                           Daily Expenses

                                                                             Average Expenses

                                                                 ‘n                       xbar                   std dev

                                                  Mr. Ellis              45                     $55                  $8

                                      Mr. Ford             45                      $60                  $3

Based on the survey, can the auditor conclude that there is a difference in the average amount charged for daily expenses by two top salesmen, Mr. Ellis and Mr. Ford. Use a =.05.

2. (p.392).Determine the critical value(s) of the test statistic for each of the following small sample tests for the comparison of two population means where the assumptions of normality and equal variance have been satisfied.                                                                        

a. Left-tailed test, a =.025, n1=13 , n2=25

b. Right-tailed test, a =.005, n1=7, n2=18

c. Two-tailed test, a =.0.10, n1=15 , n2=15

4. (p. 392) A cereal manufacturer has advertised that its product, Fiber Oat Flakes, has a lower fat content than its competitor, Bran Flakes Plus. Because of complaints from the manufacturers of Bran Flakes Plus, the FDA has decided to test the claim that Fiber Oat Flakes has a lower average fat content than Bran Flakes Plus. Several boxes of each cereal are selected and the fat content per serving is measured. The results of the study are as follows:

Fat Content of Cereals (in grams)

                                                                                      Average Fat
                                                                         n            Content, xbar s     s(std dev)

                                           Fiber Oat Flakes              16                  5                     1

                                Bran Flakes Plus              15                   6                     2

a.  What assumptions must be made in order to perform the hypothesis test?

b.  Does the study performed by the FDA substantiate the claim made by the manufacturer of Fiber Oat Flakes at a =.10?

4. (p. 395) The management for a large grocery store chain would like to determine if a new cash register will enable cashiers to process a larger number of items on average than the cash register which they are currently using. Seven cashiers are randomly selected, and the number of grocery items, which they can process in three minutes, is measured for both the old cash register and the new cash register. The results of the test are as follows:

Number of Grocery Items Processed in Three Minutes

         Cashier                                         1         2         3        4           5         6        7
         Old Cash Register                      60       70        55      75         62       52       58
         NewCashRegister                       65       71       55      75         65       57       57

 

a.  Is a paired design appropriate for the above experiment? Explain.

b.  What assumption must be made in order to perform the test of hypothesis?

c.  Does the data appear to satisfy the assumption described in part b? Why or Why not?

d.  Can the management conclude that the new cash register will allow cashiers to process a significantly larger number of items on average than the old cash register at a =.05?