Questions for Modules 45
Note: you should try these questions after you have read and understood modules 45 and chapters 712.
Note: draw the curve and label if this was a real test. You would also want to show all of your work.
1. A toothpaste manufacturer wants to determine whether the addition of a certain chemical to his toothpaste will increase its ability to fight tooth decay. Two groups of 100 people each are chosen and an experiment is conducted. Of the 100 people using the toothpaste with the chemical addition for a specified period of time, the manufacturer finds that they have an average of 8 cavities standard deviation of 3 cavities. The average number of cavities of the 100 people using the toothpaste without the chemical addition is 9 with a standard deviation of 4.
2. In order to determine whether or not there is a significant difference between the hourly wages of two companies, the following data have been accumulated.
Company A:
N1=80
x_{1}_{=$6.75}
S_{1}=$1
Company B:
N2=60
x_{2}=$6.25
S_{2}=$0.95
b. State H_{o} and H_{a} (what do we accept or reject). Level of significance is .05
x_{1} for AA children 74, S_{1}=8; MM Children, x_{2}=70, S_{2}=10 (assume normal distribution).
4. Two of the major automobile manufacturers have produced compact cars with the same size engines. We are interested in determining whether or not there is a significant difference in the MPG (miles per gallon) of the two models of cars. A random sample of 8 cars from each manufacturer is selected, and 8 drivers are selected to drive each automobile for a specified distance. The following data show the results of the test.
Driver Model A (MPG) Model B (MPG)
1 29 27
2 24 23
3 26 28
4 24 23
5 25 24
6 27 26
7 30 28
8 25 27
Test at (a=.05) to determine if there is a difference in the average MPG of the two models.
5. A large corporation wants to determine whether or not a “typing efficiency” course given at a local college can increase the typing speed of their secretaries. A sample of 6 secretaries is selected, and they are sent to take the course. The typing speeds of the secretaries in words per minute (WPM) are shown below:
Secretary Before the course (WPM) After the course (WPM)
1 65 68
2 60 62
3 61 66
4 63 66
5 64 67
6 65 67
Use (a=.05) and test to see if it can be concluded that taking the course will actually increase the average typing speeds of the secretaries.
a. What is Ho Ha, what do you reject?
b. One or two tailed test
c. Your conclusion
28,27,25,28,29,25
Use (a=.01) and test to determine whether or not the tire company is using legitimate advertising.
8. In a sample of 80 chief executive officers (CEO's) in Atlanta only 12 of them had advanced degrees.. There are indications that nationally 16% of all CEO's had advanced college degrees. . Use a .05 LOS (a=.05) in order to determine whether or not the percentage of the Atlanta CEO's who have advanced degrees is significantly less than the national average.
What is the 95% confidence interval for the population mean?
9. Last school year, the student body of a local college consisted of 30% freshmen, 24% sophomores, 26% juniors, and 20% seniors. A sample of 300 students taken from this year’s student body showed the following number of students in each classification:
Freshmen 83
Sophomores 68
Juniors 85
Seniors 64
Total=300
Has there been any significant change in the number of students in each classification between the last school year and this school year? Use a LOS=.05
b. Your conclusion?
10. A group of 500 individuals were asked to cast their votes regarding a particular issue in the Equal Rights Amendment. The following contingency table shows the results of the votes:
Sex  Undecided  Favor  Oppose  Total 
Female  180  80  40  300 
Male  150  20  30  200 
Total  330  100  70  500 
Test LOS=0.05 (a=.05) to determine if the votes cast were independent of the sex of the individuals.
a. What is H_{o} H_{a}, what do you reject?
11. Suppose that you
wish to investigate whether there really is a relationship between an
employee's performance in a company training program and the employee's
ultimate success on the job. You take a random sample of 200 cases from
the company's extensive files of employees who completed the program.
The results are as follows:
Success on Job 
Performance in Training Program 

Below Average 
Average 
Above Average 

Poor 
30 
15 
5 
Average 
10 
70 
20 
Very Good 
8 
15 
27 
Analyze your data using a 0.01 (a=.01) level of significance.