31 Practice Statistics Test Hypothesis Testing

7/29/2019 31 Practice Statistics Test Hypothesis Testing

1/17

GBS 221 Practice Statistics Test

Hypothesis Testing


2/17

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 nullhypothesis

Interpretation of your conclusion


3/17

A human resources director decided to investigateemployee perception of the fairness of two performanceevaluation methods. To test for the differences between the

two methods, 160 employees were randomly assigned tobe evaluated by one of the methods: 78 were assigned tomethod 1, where individuals provide feedback tosupervisory queries as part of the evaluation process; 82were assigned to method 2, where individuals provide self-

assessments of their work performances. Following theevaluations, employees were asked whether theyconsidered the performance evaluation fair or unfair. Ofthe 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 thereevidence that the proportion of fair ratings for theemployees in method 1 is greater than the proportion offair ratings for the employees in method 2?


4/17

A human resources

Assume the computed value of the test

statistic is: 2.89918.


5/17

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 8ounces 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 averageamount 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.)


6/17

Salad Dressing cont


statistic is -.80138


7/17

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 surfaceconditions-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 todetermine 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).


8/17

Intaglio Printing


statistic is 3.38.


9/17

4. The marketing manager for an automobilemanufacturer is interested in determiningthe proportion of new compact-car owners

who would have purchased a passenger-sideinflatable air bag if it had been available foran additional cost of $300. The managerbelieves from previous information that the

proportion is .30. Suppose that a survey of200 new compact-car owners is selectedand 79 indicate that they would have

purchased the inflatable air bags. At the .10level of significance, is there evidence thatthe population proportion is greater than.30?


10/17

Automobile Mfg.


statistic is: 2.93


11/17

5. A potential entrepreneur is

considering buying a coin-operated

laundry. The present owner claims thatover the past 5 years the average daily

revenue has been $675. A sample of 30

selected days reveals daily averagerevenue of $642, with a sample

standard deviation of $75. Is there

evidence that the daily averagerevenue is less than what the present

owner claims? (Use a .01 level of

significance.)


12/17

Coin operated laundry


statistic is -2.41


13/17

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 22are 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 resultsare on the next slide, broken down by type of

masters degree obtainedMBA versus MPH. Is

there evidence that the MBA candidates are

more preferred than the MPH candidates?

(Use a .05 level of significance.)


14/17

Assume the following results

Population 1: MBA Population 2: MPH

Mean 8.4 14.08Standard Dev 5.420332093 6.360031446

Observations 10 12

Computed value of test statistic: -2.23


15/17

7. Over the past year the vice president for

human resources at a large medical center

has run a series of three-month workshopsaimed at increasing worker motivation and

performance. To check the effectiveness of

the workshops, she selected a randomsample of 35 employees from the personnel

files and recorded their most recent annual

performance ratings along with their ratingsprior to attending the workshops.

See the next slide for a sample of the data.


16/17

A sample of the data

Employee Before After

1 59 72

2 72 74

3 89 62

4 67 74

5 81 78

6 88 86

7 71 81

8 67 72

9 78 7710 64 85

. . .

35 60 94

Motivation

Workshops

continued


17/17

Motivation workshops continued

Before After

Mean 74.54285714 79.8

Variance 80.90252101 37.16470588

Observations 35 35

Pearson Correlation -0.134202934

Hypothesized Mean Difference 0

df 34

t Stat -2.699041101

P(T

31 Practice Statistics Test Hypothesis Testing

Documents

Transcript of 31 Practice Statistics Test Hypothesis Testing