Question

The lifetimes of a certain electronic component are known to be normally distributed with a mean...

The lifetimes of a certain electronic component are known to be normally distributed with a mean of 1,400 hours and a standard deviation of 600 hours.

For a random sample of 25 components, find the probability that the sample mean is less than 1300 hours.

A

0.2033
B

0.8213
C

0.1487
D

0.5013
Math   Statistics-And-Probability   
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Homework Answers

Answer #1

Solution :

Given that ,

mean = = 1400

standard deviation = = 600

= / n = 600 / 25 = 120

P( < 1300) = P(( - ) / < (1300 - 1400) / 120)   

P(z < -0.83)

= 0.2033

Probability = 0.2033

option A is correct

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