How good are we at judging how much alcohol we have drunk? Researchers enrolled a random sample of 160 healthy adult volunteers who drink socially but are not alcoholics. A computer task was designed to measure perceptual judgment of the fullness of a glass. Each participant completed the task twice, once when the glass shown was straight and once when the glass shown was curved. For each glass, the full volume was measured on a scale of 60, such that a value of 30 corresponded to the true half. Here are the findings in summary format:
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$$\begin{array} { l l l l }
\text { Variable } & \text { Count } & \text { Mean } & \text { StDev } \
\text { Straight } & 160 & 28 & 1.50 \
\text { Curved } & 160 & 21 & 3.05 \
\text { Diff S-C } & 160 & 7 & 2.85
\end{array}$$ ?
To test whether people are better or worse at judging the true half of a glass when the glass is straight or when it is curved, which null hypothesis should we test?

Question

How good are we at judging how much alcohol we have drunk? Researchers enrolled a random sample of 160 healthy adult volunteers who drink socially but are not alcoholics. A computer task was designed to measure perceptual judgment of the fullness of a glass. Each participant completed the task twice, once when the glass shown was straight and once when the glass shown was curved. For each glass, the full volume was measured on a scale of 60, such that a value of 30 corresponded to the true half. Here are the findings in summary format:
?
?
$$\begin{array} { l l l l } 
\text { Variable } & \text { Count } & \text { Mean } & \text { StDev } \
\text { Straight } & 160 & 28 & 1.50 \
\text { Curved } & 160 & 21 & 3.05 \
\text { Diff S-C } & 160 & 7 & 2.85
\end{array}$$ ?
To test whether people are better or worse at judging the true half of a glass when the glass is straight or when it is curved, which null hypothesis should we test?

Quizplus · Accepted Answer

The correct null hypothesis to test whether people are better or worse at judging the true half of a glass when it is straight or when it is curved is to assume there is no difference in their judgment accuracy between the two conditions, which is represented by stating the mean difference (Diff S-C) equals 0.

How Good Are We at Judging How Much Alcohol We