A medical device company knows that the percentage of patients experiencing injection-site reactions with the current needle is 11%. A nurse will collect data by performing injections with this type of needle until five people experience injection-site reactions.

A geometric distribution models the number of trials needed to get the first success. Here, the nurse continues until five patients experience injection-site reactions, so the stopping point is the fifth success, not the first. Therefore, a geometric distribution is not appropriate; choice C gives the reason.

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