A company produces an electric toothbrush with a life (that time period for which it does not need a major repair) that is normally distributed with a mean of 48 months with a standard deviation of 7 months. The company wants to determine the warranty period for the toothbrush. Any toothbrush that fails within the warranty period will be replaced by the company. What should the warranty period be if the company does not want to replace more than 2% of the toothbrushes under warranty

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?

Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?

The standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?