Interpreting a Paired Sample t Test A clinical psychologist is interested in exa
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Question
Interpreting a Paired Sample t Test
A clinical psychologist is interested in examining attitudes toward the mentally ill. She believes that contact with a person who is mentally ill will improve individuals’ attitudes. To test her hypothesis, she measured attitudes toward the mentally ill before and after contact with an individual diagnosed as clinically depressed. The results are as follows:
Paired Samples Statistics
Mean
N
Std. Deviation
Std. Error Mean
Pair 1 Before
11.7143
7
1.97605
.74688
After
16.2857
7
2.81154
1.06266
Paired Samples Test
Paired Differences
95% Confidence Interval of the Difference
Mean
Std. Dev.
Std. Error Mean
Lower
Upper
t
df
Sig. (2-tailed)
Pair 1 Before - After
-4.57143
2.57275
.97241
-6.95083
-2.19203
-4.701
6
.003
a. Why is the paired samples t test appropriate for this study?
b. Study the table and comment on whether or not there is a significant treatment effect. In other words, did exposure to an individual diagnosed with mental illness improve attitudes toward the mentally ill? Explain.
c. Using the information in the tables above, write an APA style results section.
Mean
N
Std. Deviation
Std. Error Mean
Pair 1 Before
11.7143
7
1.97605
.74688
After
16.2857
7
2.81154
1.06266
Instructions Interpreting a Paired Sample t Test A clinical psychologist is interested in examining attitudes toward the mentally ill. She believes that contact with a person who is mentally ill will improve individuals' attitudes. To test her hypothesis, she measured attitudes toward the mentally ill before and after contact with an individual diagnosed as clinically depressed. The results are as follows: Paired Samples Statistics Std. Deviation .97605 2.81154 Mean Std. Error Mean Pair 1 Before 11.7143 After aired 74688 16.2857 1.06266 Paired Differences 95% confidence Interval of the Difference Mean Std. Dev. Std. Error Mean dt Sig. (2- tailed) Lower Upper t r1 -4.57143 2.57275 97241 -6.95083-2.19203-4.7016 Bcfore After 003 a. Why is the paired samples t test appropriate for this study? b. Study the table and comment on whether or not there is a significant treatment effect. In other words, did exposure to an individual diagnosed with mental illness improve attitudes toward the mentally il1? Explain. c. Using the information in the tables above, write an APA style results section.Explanation / Answer
a) The paired sample t-test, sometimes called the dependent sample t-test, is a statistical procedure used to determine whether the mean difference between two sets of observations is zero. In a paired sample t-test, each subject or entity is measured twice, resulting in pairs of observations.
Therefore, in above study a paired sample t-test is appropriate as it measures attitudes of similar individual toward menatlly ill people before and after meeting them.
(Note- A paired smaple t-test is a parametric test which has an assumption of sample number as above 30, therefore in this case, using paires sample t-test was inappropriate as here sample is 14; but as the question hasn't asked for wheter the decision was right or wrong, therefore we can answer it accordingly)
b) The results show that there is a significant treatment effect, as sig=0.003 which is less than 0.05 (p<0.05). Therefore, we can say that the treatment has a significant positive effect on the attitudes of individual.
c) From the descriptives table, it can be seen that the after group had higher mean (N= 7 , M= 16.285 , SD= 2.811) than the before group (N= 7 , M= 11.71 , SD= 1.97). Therefore, we can observe that the mean of after is higher.
From the next table we can see that the t value = -4.701, and the sig = 0.003 (p<0.05). As the sig value is less than 0.05, therefore we can observe that the treatment was significantly successfull.
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