Assignment:
Q1: The Tampa bay (Florida) Area Chamber of Commerce wanted to know whether the mean weekly salary of nurses was larger than that of school teachers. To investigate, they collected the following information on the amounts earned last week by a sample of school teachers and nurses. Is it reasonable to conclude that the mean weekly salary of nurses is higher? What is the p value?
| Teachers |
Nurses |
| 845 |
841 |
| 826 |
890 |
| 827 |
821 |
| 875 |
771 |
| 784 |
850 |
| 809 |
859 |
| 802 |
825 |
| 820 |
829 |
| 829 |
|
| 830 |
|
| 842 |
|
| 832 |
|
Null Hypothesis
Alternate Hypothesis
Choice of test
Degree of Freedom
Critical value of test
Answer to the test you calculated
p value*
Q2: The manager of a computer software company wishes to study the number of hours senior executives spend at their desktop computers by type of industry. The manager selected a sample of five executives from each of three industries. At the .05 significance level, can she conclude there is a difference in the mean number of hours spent per week by industry?
| Banking |
Retail |
Insurance |
| 12 |
8 |
10 |
| 10 |
8 |
8 |
| 10 |
6 |
6 |
| 12 |
8 |
8 |
| 10 |
10 |
10 |
Null Hypothesis
Alternate Hypothesis
Choice of test
Degree of Freedom
Critical value of test
Answer to the test you calculated
p value
Interpret your findings
Q3: The following sample observations were randomly selected.Determine the coeffiecient of correlations and the coefficient determination. Interpert the association between X and Y.
| X |
Y |
| 5 |
13 |
| 3 |
15 |
| 6 |
7 |
| 3 |
12 |
| 4 |
13 |
| 4 |
11 |
| 6 |
9 |
| 8 |
5 |
Q4: Cellon, a manufacturer of a home insulation, wants to develop guidelines for builders and consumers regarding the effects (1) of the thickness of the insulation in the attic of a home and (2) of the outdoor temperature on natural gas consumption. In the laboratory they varied the insulation thickness and temperature.
On the basis of the sample results, the regression equation is: Y-hat = 62.65 + 1.86*X(1) - 0.52*X(2)
a) How much natural gas can homeowners expect to use per months if they install 6 inches of insulation and the outdoor temperature is 40 degrees F?
b) What effect would instaling 7 inches of insulation instead of 6 have on the monthly natural gas consumption (assuming the outdoor temperature remains at 40 degrees F)?
c) Why are the regression coefficients b(1) and b(2) negative? Is this logical?
Q5: Vehicles heading west on Front Street may turn right, left, or go straight ahead at Elm Street. The city traffic engineer believes that half of the vehicles will continue straight through the intersection. Of the remaining half, equal proportions will turn right and left. Two hundred vehicles were observed, with the following results. Can we conclude that the traffic engineer is correct? Use the 0.10 significance level.
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Straight |
Right Turn |
Left Turn |
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| Frequency |
112 |
48 |
40 |
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| Null Hypothesis |
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Alternate Hypothesis |
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Alpha |
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Choice of test |
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Degree of Freedom |
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Critical value of test |
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0.10 |
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Q6: Neilsen Media Research wants to pretest a questionnaire to be mailed to several thousand viewers. One question involves the ranking of male and female college students with respect to the popularity of programs. The composite rankings of a small group of college students are:
a) Draw a scatter diagram. Let the rankings by males be X.
b) Compute the Spearman's rank-order correlation coefficient. Interpret
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Rankings |
| Program |
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Males (X) |
Females (Y) |
| "Monday Night Football" |
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1 |
5 |
| "Tonight Show with Jay Leno" |
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4 |
1 |
| "60 Minutes" |
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3 |
2 |
| "Late Show with David Letterman" |
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2 |
4 |
| "Sports Center on ESPN" |
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5 |
3 |
Q7: A normal distribution has a mean of 50 and a standard deviation of 4.
a) Compute the probability of a value between 44.0 and 55.0
b) Compute the probability of a value greater than 55.0
c) Compute the probability of a value between 52.0 and 55.0
Q7: Three defective electric toothbrushes were accidentally shipped to a drugstore by Cleanbrush Products along with 17 nondefective ones.
a) What is the probability the first two electric toothbrushes sold will be returned to the drugstore because they are defective?
b.) What is the probability the first two electric toothbrushes sold will not be defective?
Q8: A normal distribution has a mean of 50 and a standard deviation of 4.
a) Compute the probability of a value between 44.0 and 55.0
b) Compute the probability of a value greater than 55.0
c) Compute the probability of a value between 52.0 and 55.0
Q9: According to an IRS study, it takes an average of 330 minutes for taxpayers to prepare, copy, and electronically file a 1040 tax form. A consumer watchdog agency selects a random sample of 40 taxpayers and finds the standard deviation of the time to prepare, copy, and electronically file form 1040 is 80 minutes.
a) What assumption or assumptions do you need to make about the shape of the population?
b) What is the standard error of the mean in this example?
c) What is the likelihood the sample mean is greater than 320 minutes?
d) What is the likelihood the sample mean is between 320 and 350 minutes?
Q10: Bob Nale is the owner of Nale's Texaco GasTown. Bob would like to estimate the mean number of gallons of gasoline sold to his customers. From his records, he selects a random sample of 60 sales and finds the mean number of gallons sold is 8.60 and the standard deviation is 2.30 gallons.
a) What is the point estimate of the population mean?
b) Develop a 99% confidence interval for the population mean. Low Level High Level
c) Interpret the meaning of part b.
Q11: Chicken Delight claims that 90% of its orders are delivered within 10 minutes of the time the order is placed. A sample of 100 orders revealed that 82 were delivered within the promised time. At the 0.10 significance level, can we conclude that less than 90% of the orders are delivered in less than 10 minutes?
Null Hypothesis Alternate Hypothesis Alpha Choice of test Critical value of test