Question

A manufacturer knows that their items have a normally distributed lifespan, with a mean of 7.9 years, and standard deviation of 0.9 years.

If you randomly purchase one item, what is the probability it will last longer than 9 years?

Answer 1

If you randomly purchase one item, the probability it will last longer than 9 years is; 11.12%

How to find the probability from z-score?

The formula for Z-score is;

z = (x' - µ)/σ

where;

x' = sample mean

µ = population mean

σ = standard deviation

Thus;

z = (9 - 7.9)/0.9

z = 1.22

From online p-value from z-score calculator, we have;

probability = 0.1112 = 11.12%

Read more about Z-score probability at; https://brainly.com/question/25638875

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