High school juniors across the nation are preparing for the ACT exam in April. A
ID: 3182225 • Letter: H
Question
High school juniors across the nation are preparing for the ACT exam in April. A researcher wants to determine if there is a difference in ACT composite scores between students based on their study group, either Group A or Group B. The groups of students do not have any connection to each other. The following is the resulting SPSS output from a t test for two independent groups.
Are assumptions of normality met? How do you know?
Are the results of the t test significant? How do you know?
T-TEST GROUPS=StudyGroup(A B)
/MISSING=ANALYSIS
/VARIABLES=ACTscores
/CRITERIA=CI(.95).
T-Test
Group Statistics
Study Group
N
Mean
Std. Deviation
Std. Error Mean
ACT Scores
Group A
15
24.8667
1.88478
.48665
Group B
15
27.4000
1.63881
.42314
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
ACT Scores
Equal variances assumed
.056
.814
-3.928
28
.001
-2.53333
Equal variances not assumed
-3.928
27.470
.001
-2.53333
Independent Samples Test
t-test for Equality of Means
Std. Error Difference
95% Confidence Interval of the Difference
Lower
Upper
ACT Scores
Equal variances assumed
.64488
-3.85431
-1.21235
Equal variances not assumed
.64488
-3.85546
-1.21120
Group Statistics
Study Group
N
Mean
Std. Deviation
Std. Error Mean
ACT Scores
Group A
15
24.8667
1.88478
.48665
Group B
15
27.4000
1.63881
.42314
Explanation / Answer
Answer:
High school juniors across the nation are preparing for the ACT exam in April. A researcher wants to determine if there is a difference in ACT composite scores between students based on their study group, either Group A or Group B. The groups of students do not have any connection to each other. The following is the resulting SPSS output from a t test for two independent groups.
Are assumptions of normality met? How do you know?
There is no output given to infer about the assumptions of normality. We may not able to infer about this.
Test for Assumption of equality of variance:
Calculated F=0.56, P=0.814 which is > 0.05, the level of significance.
Ho is not Rejected.
We conclude that test is not significant.
Assumption of equality of variance is not violated.
Are the results of the t test significant? How do you know?
Calculated t = -3.928, P=0.001 which is less than 0.05, the level of significance.
Ho is Rejected.
We conclude that test is significant.
We conclude that there is significant difference in means of ACTS score between the two Groups.
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