Question

Quick Start Company makes 12-volt car batteries. After many years of product testing, the company knows that the average life of a Quick Start battery is normally distributed, with a mean of 45.6 months and a standard deviation of 9.3 months.
(a) If Quick Start guarantees a full refund on any battery that fails within the 36-month period after purchase, what percentage of its batteries will the company expect to replace? (Round your answer to two decimal places.)

Answer 1

do you have a TI calculator? like a TI83? or TI84?

Answer 2

yes i do.

Answer 3

ok they basically want you to find the area under the normal curve to the left of x = 36

Answer 4

so its p(x>or equal to 36) ?

Answer 5

`battery that fails within the 36-month period after purchase`

if x = battery life, then p(x < 36) is the probability we want. Basically, the probability of getting an x value less than 36, which means that the battery will be replaced

Answer 6

so its going to be normalcdf(-10^99,36,45.6,9.3)?

Answer 7

correct

Answer 8

oh thank you so much !

Answer 9

you're welcome