Suppose the number of hours a type of light bulb will burn is normally distributed with a mean 84 with a standard deviation of 9 hours. what is the probability one of these bulbs will burn for more than 90 hours? If a sample of 24 of this type of bulb is taken, what is the probability their mean number burning hours is less than 86 hours? can we apply the CLT and why?

Question

Suppose the number of hours a type of light bulb will burn is normally distributed with a mean 84 with a standard deviation of 9 hours. what is the probability one of these bulbs will burn for more than 90 hours?  If a sample of 24 of this type of bulb is taken, what is the probability their mean number burning hours is less than 86 hours? can we apply the CLT and why?

PsyDAG · Answer

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z
score.

Z = (score-mean)/SEm
SEm = SD/√n

Use same table.

What is CLT?

Jess · Answer

CLT is the central limit theorem