252hwkadd 12/01/03
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Roger Even Bove
PROBLEMS THAT APPEAR IN THE 9TH EDITION BUT NOT THE 8TH (and some from the 8th or other places. )
9.40 Suppose that in a one-tail hypothesis test where you reject H 0 only in the lower tail, you compute the value of the test statistic
z as 1.38, what is the p-value?
9.41 In Problem 9.40, what would be your statistical decision if you tested the null hypothesis at the 0.01 level of significance?
9.66 In a national poll of 811 personal computer owners, Peter D. Hart Research Associates found that 44% (357) of the PC owners
ranked sharing their credit card information as the number one concern in on-line shopping. The survey also indicated that 72% (584)
of PC owners would purchase a more secure computer if available. When given the actual dollar amount the added security would cost,
57% (462) indicated that they would pay an extra $75 for a new PC delivering a more secure on-line experience.
a. Test the null hypothesis that 50% of all PC owners in the United States rank sharing their credit card information as the
number one concern in on-line shopping versus the alternative that the percentage is not equal to 50%   .05 
b. Compute the p-value in(a) and interpret its meaning.
c. At the .05 level of significance, is there evidence that more than half of all PC owners in the United States would pay an
extra $75 for a new PC delivering as more secure on-line experience?
d. Compute the p-value in(c) and interpret its meaning.
e. At the .05 level of significance, is there evidence that more than 55% of all PC owners in the United States would pay an
extra $75 for a new PC delivering as more secure on-line experience?
f. Compute the p-value in(e) and interpret its meaning.
9.67 To handle the increased necessity of storing and organizing huge amounts of data, many companies are making large
expenditures for increased data-storage expenditures. The slowdown in the US economy, however, has many companies delaying data
storage expenditures. In July 2001, it was reported that 38% of the companies surveyed have delayed expenditures on storage
deployments because of the economic slowdown. The sample size of this survey was not disclosed.
a. Suppose that the above results were based on the responses of 50 companies. Is there evidence at the .01 level of
significance that less than half of all companies are delaying data-storage expenditures?
b. Compute the p-value in(a) and interpret its meaning.
c. Suppose that the above results were based on the responses of 100 companies. Is there evidence at the .01 level of
significance that less than half of all companies are delaying data-storage expenditures?
d. Compute the p-value in(c) and interpret its meaning.
e. Compare your answers in (a) and (b) with your answers to (c) and (d). Explain the effect that sample size has on statistical
significance.
f. What ethical issues are raised when one fails to report the sample size used in a survey?
10.32 HomeGrocer.com vs. local Seattle supermarkets.
Products
1
2
3
4
5
6
7
8
Tide High Efficiency, 64 oz.
Oreo Cookies, 20 oz.
Formula 409 Cleaner, 22 oz.
Pampers Newborn Diapers, 40 count
Coke Classic, dozen 12 oz. Cans
Colgate Total Toothpaste, 7.8 oz.
Tropicana Orange Juice, 64 oz.
Cheerrios Whole Grain Cereal, 20 oz.
HomeGrocer
6.99
3.29
2.59
10.79
3.99
3.49
3.59
4.29
Supermarkets
6.99
3.49
2.69
10.99
3.59
3.49
3.49
3.99
a. At the 0.05 level, is there evidence of a difference in the average price for products purchased from the two vendors?
b. Compute the p-value in(a) and interpret its meaning.
c. Set up a 95% confidence interval estimate of the difference in the average price for products purchased from the two
vendors?
d. Compare the results in (a) and (c).
12.7 Of 56 white workers terminated, 29 claimed bias. Of 407 black workers terminated, 126 claimed bias.
a. At the 5% significance level, is there evidence that white workers are more likely to claim bias than black workers?
b. Find and interpret the p-value in a.
12.8 500 African Americans and 500 whites (all with incomes above $50000) were surveyed with the result that 74% of the AfricanAmericans and 84% of the whites owned stocks.
a. At the 5% significance level, is there a significant difference between the proportion of African Americans and the
proportion of whites who own stocks?
b. Find and interpret the p-value in a.
c. Set up a 95% confidence interval for the difference between the two proportions.
D6a Given: H 0 :  12   22 , H 1 :  12   22 , n1  16 , n 2  21, s12  100 and s 22  400 . Test the hypotheses using only right tail
tests.   .05 .
12.23 The results of a Gallup phone survey appear below. Consumers were asked if they objected to having their medical records
shared with different types of organizations. Results follow.
O
Ins Cos Pharm Research
Yes  820
590
670 


No  180
410
330 
a) Is the proportion of people who object different for different institutions?   .05 .
b) If appropriate, use the Marascuilo procedure to determine which organizations are different. Discuss.
12.49 The manager of a computer network has the following data on service interruptions per day over the last 500 days. Does it
follow a Poisson distribution?   .01
Interruptions Number
per day
of days
0
160
1
175
2
86
3
41
4
5
6
Total
18
12
8
500
12.52 A random sample of 500 car batteries revealed the following distribution of battery life in years. If x  2.80 and s  0.97 ,
does it follow a Normal distribution?   .05 
Life
Frequency
0  under 1
12
1  under 2
94
2  under 3
170
3  under 4
188
4  under 5
28
5  under 6
Total
8
500
14.4 Computer Output.
————— 11/20/2003 11:23:07 PM ————————————————————
Welcome to Minitab, press F1 for help.
MTB > Retrieve "C:\Berenson\Data_Files-9th\Minitab\Warecost.MTW".
2
Retrieving worksheet from file: C:\Berenson\Data_Files-9th\Minitab\Warecost.MTW
# Worksheet was saved on Mon Apr 27 1998
Results for: Warecost.MTW
MTB > Regress c1 2 c2 c3;
SUBC>
Constant;
SUBC>
VIF;
SUBC>
Brief 3.
Regression Analysis: DistCost versus Sales, Orders
Minitab regression Output.
The regression equation is
DistCost = - 2.73 + 0.0471 Sales + 0.0119 Orders
Predictor
Constant
Sales
Orders
Coef
-2.728
0.04711
0.011947
S = 4.766
SE Coef
6.158
0.02033
0.002249
R-Sq = 87.6%
T
-0.44
2.32
5.31
P
0.662
0.031
0.000
VIF
2.8
2.8
R-Sq(adj) = 86.4%
Analysis of Variance
Source
Regression
Residual Error
Total
Source
Sales
Orders
Obs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
DF
2
21
23
SS
3368.1
477.0
3845.1
DF
1
1
Sales
386
446
512
401
457
458
301
484
517
503
535
353
372
328
408
491
527
444
623
596
463
389
547
415
MS
1684.0
22.7
F
74.13
P
0.000
Seq SS
2726.8
641.3
DistCost
52.950
71.660
85.580
63.690
72.810
68.440
52.460
70.770
82.030
74.390
70.840
54.080
62.980
72.300
58.990
79.380
94.440
59.740
90.500
93.240
69.330
53.710
89.180
66.800
Fit
63.425
63.755
84.820
67.082
70.127
67.796
49.839
77.528
84.196
77.503
75.199
48.800
62.311
65.626
63.852
75.145
88.789
59.407
87.302
93.867
70.087
59.898
87.401
66.535
SE Fit
1.332
1.511
1.656
1.332
0.999
1.193
2.134
1.139
1.525
1.126
1.838
2.277
1.483
2.847
1.152
1.069
2.004
2.155
2.535
2.097
1.049
1.349
1.657
1.107
Residual
-10.475
7.905
0.760
-3.392
2.683
0.644
2.621
-6.758
-2.166
-3.113
-4.359
5.280
0.669
6.674
-4.862
4.235
5.651
0.333
3.198
-0.627
-0.757
-6.188
1.779
0.265
St Resid
-2.29R
1.75
0.17
-0.74
0.58
0.14
0.62
-1.46
-0.48
-0.67
-0.99
1.26
0.15
1.75
-1.05
0.91
1.31
0.08
0.79
-0.15
-0.16
-1.35
0.40
0.06
R denotes an observation with a large standardized residual
MTB > Print c1-c3
Data Display
Original Data
Row
DistCost
Sales
Orders
1
2
52.95
71.66
386
446
4015
3806
3
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
85.58
63.69
72.81
68.44
52.46
70.77
82.03
74.39
70.84
54.08
62.98
72.30
58.99
79.38
94.44
59.74
90.50
93.24
69.33
53.71
89.18
66.80
512
401
457
458
301
484
517
503
535
353
372
328
408
491
527
444
623
596
463
389
547
415
5309
4262
4296
4097
3213
4809
5237
4732
4413
2921
3977
4428
3964
4582
5582
3450
5079
5735
4269
3708
5387
4161
MTB > Save "C:\Documents and Settings\RBOVE.WCUPANET\My Documents\Drive D\MINITAB\Warecost.MTW";
SUBC>
Replace.
Saving file as: C:\Documents and Settings\RBOVE.WCUPANET\My Documents\Drive D\MINITAB\Warecost.MTW
MTB > Stop.
13.36 Suppose that you are testing the null hypothesis that there is no relationship between x and y . Assume n  20 and that
SSR  60 and SSE  40 .
a. What is the value of the F test statistic?
b. At the 5% significance level what is the critical value of F?
c. Based on the answers to a) and b) what statistical decision should be made?
d. Calculate the correlation coefficient from R 2 by assuming that the slope b1 is negative.
e. At the 5% significance level, is there significant correlation between x and y ?
4