To determine the degrees of freedom (df) for an independent-measures t-test, we can use the formula:
[tex]\[ \text{df} = N - 2 \][/tex]
where \( N \) is the total number of participants in the study.
In this case, the total number of participants ( \( N \) ) is given as 40. Applying the formula, we get:
[tex]\[ \text{df} = 40 - 2 \][/tex]
[tex]\[ \text{df} = 38 \][/tex]
Therefore, the correct df value for the t statistic for this study is:
C. 38
