Jessica Salas,president of Salas Products,is reviewing the warranty policy for her company's new model of automobile batteries. Life tests performed on a sample of 100 batteries indicated: (1)an average life of 75 months,(2)a standard deviation of 5 months,and (3)a bell shaped battery life distribution.Approximately 95% of the batteries will last between ________________.
A) 70 and 80 months
B) 60 and 90 months
C) 65 and 85 months
D) 55 and 95 months
E) 60 and 100 months

Question

Quizplus · Accepted Answer

Since the distribution of battery life is bell-shaped and we know the standard deviation, we can use the empirical rule (also known as the 68-95-99.7 rule) to estimate the percentage of batteries that will last between certain values. According to the rule:

- Approximately 68% of the batteries will last between (75 - 5) and (75 + 5) months, which is between 70 and 80 months.
- Approximately 95% of the batteries will last between (75 - 2*5) and (75 + 2*5) months, which is between 65 and 85 months.

Therefore, the best choice is C, which includes the range of battery life that covers approximately 95% of the sample. The other choices either include too many or too few months, based on the empirical rule.

Jessica Salas,president of Salas Products,is Reviewing the Warranty Policy for Her