Stats Homework

once or in intervals. One group of 12 participants took a test after studying for

one hour continuously. The other group of 12 participants took a test after

studying for three twenty minute sessions. The first group had a mean score of

75 and a variance of 120. The second group had a mean score of 86 and a

variance of 100.

a. What is the calculated t value? Are the mean test scores of these two groups

significantly different at the .05 level?

b. What would the t value be if there were only 6 participants in each group?

Would the scores be significant at the .05 level?

Illowsky Ch.9 #71

71. Previously, an organization reported that teenagers spent 4.5 hours per week, on average, on the phone. The organization

thinks that, currently, the mean is higher. Fifteen randomly chosen teenagers were asked how many hours per week they

spend on the phone. The sample mean was 4.75 hours with a sample standard deviation of 2.0. Conduct a hypothesis test,

the Type I error is:

a. to conclude that the current mean hours per week is higher than 4.5, when in fact, it is higher

b. to conclude that the current mean hours per week is higher than 4.5, when in fact, it is the same

c. to conclude that the mean hours per week currently is 4.5, when in fact, it is higher

d. to conclude that the mean hours per week currently is no higher than 4.5, when in fact, it is not higher

Illosky Ch. 9 #77

77. An article in the San Jose Mercury News stated that students in the California state university system take 4.5 years, on

average, to finish their undergraduate degrees. Suppose you believe that the mean time is longer. You conduct a survey of

49 students and obtain a sample mean of 5.1 with a sample standard deviation of 1.2. Do the data support your claim at the

1% level?

Illosky Ch. 10 #91

91. A powder diet is tested on 49 people, and a liquid diet is tested on 36 different people. Of interest is whether the liquid

diet yields a higher mean weight loss than the powder diet. The powder diet group had a mean weight loss of 42 pounds

with a standard deviation of 12 pounds. The liquid diet group had a mean weight loss of 45 pounds with a standard deviation

of 14 pounds.

Illosky Ch. 10, #120

120. A golf instructor is interested in determining if her new technique for improving players’ golf scores is effective. She takes four new students. She records their 18-hole scores before learning the technique and then after having taken her class.

She conducts a hypothesis test. The data are as follows.

Player 1 Player 2 Player 3 Player 4

Mean score before class 83 78 93 87

Mean score after class 80 80 86 86

The correct decision is:

a. Reject H0.

b. Do not reject the H0.

Week 7

Illowsky Ch 11. #102

102. Do men and women select different breakfasts? The breakfasts ordered by randomly selected men and women at a popular breakfast place is shown in

Table 11.55. Conduct a test for homogeneity at a 5% level of significance.

French Toast Pancakes Waffles Omelettes

Men 47 35 28 53

Women 65 59 55 60

Illowsky, Ch 12, #66

66. Can a coefficient of determination be negative? Why or why not?

Illowsky, Ch 11 #70

70. The standard deviation of the chi-square distribution is twice the mean.

Lane, Ch 14, #2

2. The formula for a regression equation is Y’ = 2X + 9.

a. What would be the predicted score for a person scoring 6 on X?

b. If someone’s predicted score was 14, what was this person’s score on X?

Lane, Ch 14 #6

6. For the X,Y data below, compute:

a. r and determine if it is significantly different from zero.

b. the slope of the regression line and test if it differs significantly from zero.

c. the 95% confidence interval for the slope.

Week 8

Illowsky Ch, 13 #69

69. A researcher wants to know if the mean times (in minutes) that people watch their favorite news station are the same.

Suppose that Table 13.24 shows the results of a study.

CNN FOX Local

45 15 72

12 43 37

18 68 56

38 50 60

23 31 51

35 22

Illowsky Ch. 13 #71

71. Are the mean number of times a month a person eats out the same for whites, blacks, Hispanics and Asians? Suppose

that Table 13.26 shows the results of a study.

White Black Hispanic Asian

6 4 7 8

8 1 3 3

2 5 5 5

4 2 4 1

6 6 7

Table 13.26

Illowsky Ch. 13, #77

77. A grassroots group opposed to a proposed increase in the gas tax claimed that the increase would hurt working-class people the most, since they commute the farthest to work. Suppose that the group randomly surveyed 24 individuals and asked them their daily one-way commuting mileage.

The results are as follows.

working-class professional (middle incomes) professional (wealthy)

17.8 16.5 8.5

26.7 17.4 6.3

Illowsky Ch. 13, #81

81. Is the variance for the amount of money, in dollars, that shoppers spend on Saturdays at the mall the same as the variance for the amount of money that shoppers spend on Sundays at the mall?

Suppose that the Table 13.34 shows the results of a study.

Saturday Sunday Saturday Sunday

75 44 62 137

18 58 0 82

150 61 124 39

94 19 50 127

62 99 31 141

73 60 118 73

89

Lane Ch. 15 #10

10. If an experiment is conducted with 5 conditions and 6 subjects in each

condition, what are dfn and dfe?