GBS 221 Practice Statistics Test

1. GBS 221 Practice Statistics Test Hypothesis Testing

2. For each of the following problems determine: Type of problem Null Hypothesis Alternate Hypothesis Critical Value(s)������� Test Statistic����� Conclusion to accept or reject the null hypothesis�� Interpretation of your conclusion�����

3. A human resources director decided to investigate employee perception of the fairness of two performance evaluation methods. To test for the differences between the two methods, 160 employees were randomly assigned to be evaluated by one of the methods: 78 were assigned to method 1, where individuals provide feedback to supervisory queries as part of the evaluation process; 82 were assigned to method 2, where individuals provide self- assessments of their work performances. Following the evaluations, employees were asked whether they considered the performance evaluation fair or unfair. Of the 78 employees in method 1, there were 63 fair ratings. Of the 82 employees in method 2, there were 49 fair ratings. Using a .05 level of significance, is there evidence that the proportion of fair ratings for the employees in method 1 is greater than the proportion of fair ratings for the employees in method 2?

4. A human resources� Assume the computed value of the test statistic is: 2.89918.

5. 2. A manufacturer of salad dressings uses machines to dispense liquid ingredients into bottles that move along a filling line. The machine that dispenses dressings is working properly when 8 ounces are dispensed. The standard deviation of the process is 0.15 ounce. A sample of 50 bottles is selected periodically, and the filling line is stopped if there is evidence that the average amount dispensed is different from 8 ounces. Suppose that the average amount dispensed in a particular sample of 50 bottles is 7.983 ounces. Is there evidence that the population average amount is different from 8 ounces? (Use a .05 level of significance.)

6. Salad Dressing con�t� Assume the computed value of the test statistic is -.80138

7. 3. In intaglio printing, a design or figure is carved beneath the surface of hard metal or stone. Suppose that an experiment is designed to compare differences in average surface hardness of steel plates used in intaglio printing (measured in indentation numbers) based on two different surface conditions-untreated versus treated by light polishing with emery paper. If in the experiment 40 steel plates are randomly assigned, 20 that are untreated and 20 that are lightly polished, use a .05 level of significance to determine whether there is evidence of a significant treatment effect (i.e., a significant difference in average surface hardness between the untreated and the polished steel plates) if the sample mean for the untreated plates is 166.0 (sample standard deviation is 10.2) and the sample mean for the polished plates is 156.9 (sample standard deviation is 6.4).

8. Intaglio Printing Assume the computed value of the test statistic is 3.38.

9. 4. The marketing manager for an automobile manufacturer is interested in determining the proportion of new compact-car owners who would have purchased a passenger-side inflatable air bag if it had been available for an additional cost of $300. The manager believes from previous information that the proportion is .30. Suppose that a survey of 200 new compact-car owners is selected and 79 indicate that they would have purchased the inflatable air bags. At the .10 level of significance, is there evidence that the population proportion is greater than .30?

10. Automobile Mfg. Assume the computed value of the test statistic is: 2.93

11. 5. A potential entrepreneur is considering buying a coin-operated laundry. The present owner claims that over the past 5 years the average daily revenue has been $675. A sample of 30 selected days reveals daily average revenue of $642, with a sample standard deviation of $75. Is there evidence that the daily average revenue is less than what the present owner claims? (Use a .01 level of significance.)

12. Coin operated laundry Assume the computed value of the test statistic is -2.41

13. 6. The director of human resources at a 1,200-bed New York City hospital is evaluating candidates for the position of administrator of the billings and payments department. Among the applicants 22 are invited for interviews. Following the interviews, the rankings (1= most preferred) of the candidates (based on interview, academic record, and prior experience) are determined. The results are on the next slide, broken down by type of masters degree obtained � MBA versus MPH. Is there evidence that the MBA candidates are more preferred than the MPH candidates? (Use a .05 level of significance.)

15. 7. Over the past year the vice president for human resources at a large medical center has run a series of three-month workshops aimed at increasing worker motivation and performance. To check the effectiveness of the workshops, she selected a random sample of 35 employees from the personnel files and recorded their most recent annual performance ratings along with their ratings prior to attending the workshops. See the next slide for a sample of the data.