2Does Sexual Frustration Increase the Desire for Alcohol? Apparently, sexual
frustration increases the desire for alcohol, at least in fruit flies.
Scientists \(^{35}\) randomly put 24 fruit flies into one of two situations. The
12 fruit flies in the "mating" group were allowed to mate freely with many
available females eager to mate. The 12 in the "rejected" group were put with
females that had already mated and thus rejected any courtship advances. After
four days of either freely mating or constant rejection, the fruit flies spent
three days with unlimited access to both normal fruit fly food and the same
food soaked in alcohol. The percent of time each fly chose the alcoholic food
was measured. The fruit flies that had freely mated chose the two types of
food about equally often, choosing the alcohol variety on average \(47 \%\) of
the time. The rejected males, however, showed a strong preference for the food
soaked in alcohol, selecting it on average \(73 \%\) of the time. (The study was
designed to study a chemical in the brain called neuropeptide that might play
a role in addiction.)
(a) Is this an experiment or an observational study?
(b) What are the cases in this study? What are the variables? Which is the
explanatory variable and which is the response variable?
(c) We are interested in the difference in means, where the means measure the
average percent preference for alcohol \((0.47\) and 0.73 in this case). Find
the difference in means and give the correct notation for your answer, using
the correct notation for a mean, subscripts to identify groups, and a minus
sign.
(d) Can we conclude that rejection increases a male fruit fly's desire for
alcohol? Explain.
