A Psychologist Wishes to Determine Whether Drinking Coffee Improves One's

Multiple Choice

A psychologist wishes to determine whether drinking coffee improves one's mood. The psychologist hangs out at the Café Coffay and asks customers to fill out a 10-point good-mood, bad-mood questionnaire (where 10 = great mood and 1 = bad mood) before and after their first cup of coffee that day. The research question is whether there is any evidence that drinking coffee improves mood. $\begin{array}{lll}&\text { Before Mood Rating }&\text { After Mood Rating }\\\hline \text { Participant 1 } & 5 & 9 \\\text { Participant 2 } & 3 & 8 \\\text { Participant 3 } & 9 & 9 \\\text { Participant 4 } & 3 & 8 \\\text { Participant 5 } & 2 & 7 \\\text { Participant 6 } & 4 & 9 \\\text { Participant 7 } & 1 & 10\\\text { Participant 8 } & 8 & 8 \\\text { Participant 9 } & 6 & 5 \\\text { Participant 10 } & 7 & 7 \\\text { Participant 11 } & 4 & 3 \\\text { Participant 12 } & 3 & 10 \\\text { Participant 13 } & 8 & 7 \\\text { Participant 14 } & 7 & 9 \\\text { Participant 15 } & 5 & 9\\\hline\end{array}$
-Assume this t test had a nondirectional alternative hypothesis, and we will use the conventional level of statistical significance.The critical value (plus and minus) of the t test for this problem (obtained from Appendix B: t distribution) is

A) 2.145
B) 2.977
C) 4.140
D) 2.131