Inferential Statistics
An independent-samples t-test was used to test the difference between the mean ratings of the charismatic-teacher-reputation condition and the punitive-teacher-reputation condition. The output from SPSS is shown below.
t-test for Equality of Means
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Variances | t-value | df | 2-Tail Sig | SE of Diff | 95% CI for Diff |
---|---|---|---|---|---|
Equal
|
2.45
|
47
|
0.018
|
0.154
|
(0.068, 0.686)
|
Unequal
|
2.45
|
46.83
|
0.018
|
0.154
|
(0.068, 0.687)
|
SPSS automatically computes the test under the assumption that the variances are equal (row 1) and without making this assumption (row 2). For the present data, the sample variances are nearly identical so the two tests yield the same results. The t test of the difference between means (Charismatic - Punitive) results in a t of 2.45.
Is this value of t is significant at the 0.05 level?The lower limit on the difference between the charismatic instructor's and the punitive instuctor's rating based on the 95% confidence interval is
0.018
0.154
0.068
0.686
0.687
Assumptions
The t test and the analysis of variance both assume: