Paper Details

A volunteer working at an animal shelter conducted a study of the effect of catnip on cats at the shelter. She recorded the number of “negative interactions” each of 15 cats made in 15-minute periods before and after being given a teaspoon of catnip. The paired measurements were collected on the same day within 30 minutes of one another; the data are given in the accompanying table.29

(a) Construct a 95% confidence interval for the difference in mean number of negative interactions.

(b) Construct a 95% confidence interval the wrong way, using the independent-samples method. How does this interval differ from the one obtained in part (a)?