PSY315 Week4 Worksheet[1]

Week 4 Practice Worksheet
PSY/315 Version 6
1
University of Phoenix Material
Week 4 Practice Worksheet
Prepare a written response to the following questions.
Chapters 9 &11
1. Two boats, the Prada (Italy) and the Oracle (USA), are competing for a spot in the upcoming America’s Cup
race. They race over a part of the course several times. The sample times in minutes for the Prada were:
12.9, 12.5, 11.0, 13.3, 11.2, 11.4, 11.6, 12.3, 14.2, and 11.3. The sample times in minutes for the Oracle
were: 14.1, 14.1, 14.2, 17.4, 15.8, 16.7, 16.1, 13.3, 13.4, 13.6, 10.8, and 19.0. For data analysis, the
appropriate test is the t-Test: Two-Sample Assuming Unequal Variances.
The next table shows the results of this independent t-test. At the .05 significance level, can we
conclude that there is a difference in their mean times? Explain these results to a person who knows
about the t test for a single sample but is unfamiliar with the t test for independent means.
Hypothesis Test: Independent Groups (t-test, unequal variance)
Prada
12.170
1.056
10
Oracle
14.875
2.208
12
16
-2.7050
0.7196
0
-3.76
.0017
-4.2304
-1.1796
1.5254
mean
std. dev.
n
df
difference (Prada - Oracle)
standard error of difference
hypothesized difference
t
p-value (two-tailed)
confidence interval 95.% lower
confidence interval 95.% upper
margin of error
2. The Willow Run Outlet Mall has two Haggar Outlet Stores, one located on Peach Street and the other on
Plum Street. The two stores are laid out differently, but both store managers claim their layout maximizes the
amounts customers will purchase on impulse. A sample of ten customers at the Peach Street store revealed
they spent the following amounts more than planned: $17.58, $19.73, $12.61, $17.79, $16.22, $15.82,
$15.40, $15.86, $11.82, $15.85. A sample of fourteen customers at the Plum Street store revealed they
spent the following amounts more than they planned when they entered the store: $18.19, $20.22, $17.38,
$17.96, $23.92, $15.87, $16.47, $15.96, $16.79, $16.74, $21.40, $20.57, $19.79, $14.83. For Data Analysis,
a t-Test: Two-Sample Assuming Unequal Variances was used.
At the .01 significance level is there a difference in the mean amount purchased on an impulse at the
two stores? Explain these results to a person who knows about the t test for a single sample but is
Copyright ©2013 by Pearson Education, Inc. All rights reserved. Used with permission
Week 4 Practice Worksheet
PSY/315 Version 6
2
unfamiliar with the t test for independent means.
Hypothesis Test: Independent Groups (t-test, unequal variance)
Peach Street
15.8680
2.3306
10
Plum Street
18.2921
2.5527
14
mean
std. dev.
n
20
df
difference (Peach Street Plum Street)
standard error of difference
hypothesized difference
-2.42414
1.00431
0
-2.41
.0255
t
p-value (two-tailed)
confidence interval 99.%
lower
confidence interval 99.%
upper
-5.28173
0.43345
2.85759
margin of error
3. Fry Brothers heating and Air Conditioning, Inc. employs Larry Clark and George Murnen to make service
calls to repair furnaces and air conditioning units in homes. Tom Fry, the owner, would like to know whether
there is a difference in the mean number of service calls they make per day. Assume the population
standard deviation for Larry Clark is 1.05 calls per day and 1.23 calls per day for George Murnen. A random
sample of 40 days last year showed that Larry Clark made an average of 4.77 calls per day. For a sample of
50 days George Murnen made an average of 5.02 calls per day. At the .05 significance level, is there a
difference in the mean number of calls per day between the two employees? What is the p-value?
Hypothesis Test: Independent Groups (t-test, pooled variance)
Larry
4.77
1.05
40
George
5.02
1.23
50
88
-0.25000
1.33102
1.15370
0.24474
0
-1.02
.3098
mean
std. dev.
n
df
difference (Larry - George)
pooled variance
pooled std. dev.
standard error of difference
hypothesized difference
t
p-value (two-tailed)
Copyright ©2013 by Pearson Education, Inc. All rights reserved. Used with permission
Week 4 Practice Worksheet
PSY/315 Version 6
-0.73636
0.23636
3
confidence interval 95.% lower
confidence interval 95.% upper
0.48636
margin of error
Chapters 11 & 12
4. A consumer organization wants to know if there is a difference in the price of a particular toy at three
different types of stores. The price of the toy was checked in a sample of five discount toy stores, five variety
stores, and five department stores. The results are shown below.
Discount toy
Variety
Department
$12
15
19
13
17
17
14
14
16
12
18
20
15
17
19
An ANOVA was run and the results are shown below. At the .05 significance level, is there a difference in the
mean prices between the three stores? What is the p-value? Explain why an ANOVA was used to analyze this
problem.
One factor ANOVA
Mean
n
Std. Dev
13.2
5
1.30
Discount
Toys
16.2
5
1.64
Variety
18.2
15.9
5
15
1.64
2.56
Department
Total
SS
63.33
28.40
91.73
df
2
12
14
MS
31.667
2.367
ANOVA table
Source
Treatment
Error
Total
F
13.38
pvalue
.0009
Copyright ©2013 by Pearson Education, Inc. All rights reserved. Used with permission
Week 4 Practice Worksheet
PSY/315 Version 6
4
5. A physician who specializes in weight control has three different diets she recommends. As an experiment,
she randomly selected 15 patients and then assigned 5 to each diet. After three weeks the following weight
losses, in pounds, were noted. At the .05 significance level, can she conclude that there is a difference in the
mean amount of weight loss among the three diets?
Plan A
Plan B
Plan C
5
6
7
7
7
8
4
7
9
5
5
8
4
6
9
An ANOVA was run and the results are shown below. At the .01 significance level, is there a difference in the
weight loss between the three plans? What is the p-value? What can you do to determine exactly where the
difference is?
One factor ANOVA
Mean
n
Std.
Dev
5.0
5
1.22
6.2
5
0.84
8.2
6.5
5
15
0.84
1.64
SS
26.13
11.60
37.73
df
2
12
14
MS
13.067
0.967
Plan
A
Plan
B
Plan
C
Total
ANOVA table
Source
Treatment
Error
Total
F
13.52
pvalue
.0008
Copyright ©2013 by Pearson Education, Inc. All rights reserved. Used with permission

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