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 68% 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

The correct answer is based on the empirical rule (or 68-95-99.7 rule) for a bell-shaped distribution, which states that approximately 68% of the data falls within one standard deviation of the mean. Given a mean of 75 months and a standard deviation of 5 months, 68% of the batteries will last between 70 (75-5) and 80 (75+5) months.

Jessica Salas, President of Salas Products, Is Reviewing the Warranty