还有题目呢

来源: 于 2010-04-01 08:58:38 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

A telemarketer makes six phone calls per hour and is able to make a sale on 30 oercent of these conacts. duromg the next two hours, find
1. the probability of making exactly four sales
2. the probability of making no sales
3. the probability of making exactly two sales
d. the mean number of sales in the two-hour period