PSYC 355 Independent Samples and Paired Samples T-Tests Analysis in SPSS
An SPSS-based analysis comparing independent and paired samples using T-tests.
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PSYC 355
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PSYC 355 Independent Samples and Paired Samples T-Tests Analysis in
SPSS
SPSS HOMEWORK 2 INSTRUCTIONS
INDEPENDENT SAMPLES T-TESTS
Part 1:
Green & Salkind: Lesson 24, Exercises 1–5
The following helpful tips are numbered to correspond with the exercise number to which they
refer:
1. Type these values out underneath your copied and pasted output. (3 pts)
Group Statistics
Weight
classification N Mean Std. Deviation Std. Error Mean
Time spent eating Big Mac
specials in seconds
overweight 10 589.00 42.615 13.476
normal weight 30 698.40 82.949 15.144
Independent Samples Test
Levene's Test for
Equality of
Variances t-test for Equality of Means
F Sig. t df
Sig. (2-
tailed)
Mean
Difference
Std. Error
Difference
95% Confidence
Interval of the
Difference
Lower Upper
Time spent
eating Big Mac
specials in
seconds
Equal
variances
assumed
2.745 .106 -3.975 38 .000 -109.400 27.522 -165.116 -53.684
Equal
variances not
assumed
-5.397 30.828 .000 -109.400 20.272 -150.754 -68.046
T-value for equal variances assumed: -3.95
T-value for equal variances not assumed: -5.397
2. Instead of identifying these values on your output, as the text states, write them in your
Word file as written answers for #2 a, b, and c. (3 pts, 1 point for each letter)
Page 1 of 7
PSYC 355 Independent Samples and Paired Samples T-Tests Analysis in
SPSS
SPSS HOMEWORK 2 INSTRUCTIONS
INDEPENDENT SAMPLES T-TESTS
Part 1:
Green & Salkind: Lesson 24, Exercises 1–5
The following helpful tips are numbered to correspond with the exercise number to which they
refer:
1. Type these values out underneath your copied and pasted output. (3 pts)
Group Statistics
Weight
classification N Mean Std. Deviation Std. Error Mean
Time spent eating Big Mac
specials in seconds
overweight 10 589.00 42.615 13.476
normal weight 30 698.40 82.949 15.144
Independent Samples Test
Levene's Test for
Equality of
Variances t-test for Equality of Means
F Sig. t df
Sig. (2-
tailed)
Mean
Difference
Std. Error
Difference
95% Confidence
Interval of the
Difference
Lower Upper
Time spent
eating Big Mac
specials in
seconds
Equal
variances
assumed
2.745 .106 -3.975 38 .000 -109.400 27.522 -165.116 -53.684
Equal
variances not
assumed
-5.397 30.828 .000 -109.400 20.272 -150.754 -68.046
T-value for equal variances assumed: -3.95
T-value for equal variances not assumed: -5.397
2. Instead of identifying these values on your output, as the text states, write them in your
Word file as written answers for #2 a, b, and c. (3 pts, 1 point for each letter)
PSYC 355
Page 2 of 7
a. The mean eating time for overweight individuals was 589 seconds.
b. The standard deviation for normal weight individuals was 82.95.
c. c. The F-statistic, which shows if the assumption of homogeneity of variances has
been violated, was 2.745 with a p-value of 0.106. The assumption was not
violated
3. The effect size statistic must be computed by hand (or calculator). Use the second
“easier” formula for d, found in the section on Effect Size Statistics in this lesson. (3 pts)
d = t √ ((N1+N2) / (N1N2))
d = -3.975 √ ((10+30) / (10*30))
d = -3.975 √ (40/300)
d = -3.975 (0.365)
d = -1.451
4. An independent t-test showed that there was a significant difference between the mean
eating time for the two groups, t (38) = - 3.975, p < 0.001, d = -1.451, in this sample. The
mean eating time of a Big Mac special for overweight individuals (M = 589, SD = 42.6)
was shorter than the mean eating time for normal weight individuals (M = 698, SD =
82.9). The alternative hypothesis that overweight individuals take less time to eat a Big
Mac than normal weight individuals should be accepted. The null hypothesis that there is
no difference in the eating time of the two groups should be rejected.
5. Create a boxplot (not an error bar graph) using the following steps (covered also in
Lesson 21). (3 pts)
Time spent eating Big Mac specials in seconds by Weight Category
Page 2 of 7
a. The mean eating time for overweight individuals was 589 seconds.
b. The standard deviation for normal weight individuals was 82.95.
c. c. The F-statistic, which shows if the assumption of homogeneity of variances has
been violated, was 2.745 with a p-value of 0.106. The assumption was not
violated
3. The effect size statistic must be computed by hand (or calculator). Use the second
“easier” formula for d, found in the section on Effect Size Statistics in this lesson. (3 pts)
d = t √ ((N1+N2) / (N1N2))
d = -3.975 √ ((10+30) / (10*30))
d = -3.975 √ (40/300)
d = -3.975 (0.365)
d = -1.451
4. An independent t-test showed that there was a significant difference between the mean
eating time for the two groups, t (38) = - 3.975, p < 0.001, d = -1.451, in this sample. The
mean eating time of a Big Mac special for overweight individuals (M = 589, SD = 42.6)
was shorter than the mean eating time for normal weight individuals (M = 698, SD =
82.9). The alternative hypothesis that overweight individuals take less time to eat a Big
Mac than normal weight individuals should be accepted. The null hypothesis that there is
no difference in the eating time of the two groups should be rejected.
5. Create a boxplot (not an error bar graph) using the following steps (covered also in
Lesson 21). (3 pts)
Time spent eating Big Mac specials in seconds by Weight Category
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Document Details
University
American Public University
Subject
Psychology