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

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. $\begin{array}{lll}&\text { Before Mood Rating }&\text { After Mood Rating }\\\hline \text { Participant 1 } & 5 & 9 \\\text { Participant 2 } & 3 & 8 \\\text { Participant 3 } & 9 & 9 \\\text { Participant 4 } & 3 & 8 \\\text { Participant 5 } & 2 & 7 \\\text { Participant 6 } & 4 & 9 \\\text { Participant 7 } & 1 & 10\\\text { Participant 8 } & 8 & 8 \\\text { Participant 9 } & 6 & 5 \\\text { Participant 10 } & 7 & 7 \\\text { Participant 11 } & 4 & 3 \\\text { Participant 12 } & 3 & 10 \\\text { Participant 13 } & 8 & 7 \\\text { Participant 14 } & 7 & 9 \\\text { Participant 15 } & 5 & 9\\\hline\end{array}$
-In nonstatistical language, what can be concluded?

A) it appears that coffee drinking is associated with improved mood
B) coffee drinking does not cause mood improvement
C) coffee drinking is correlated with people's moods
D) the null hypothesis is retained