A&X Electrical makes a lamp. The Research department found that the life of the lamp is normally distributed with a mean of 5000 hours and a standard deviation of 450 hours.

1. What is the probability a sample of 10 lamps will have a mean life less than 4950 hours?

is the answer .3632?

Question

A&X Electrical makes a lamp.  The Research department found that the life of the lamp is normally distributed with a mean of 5000 hours and a standard deviation of 450 hours.


1.	What is the probability a sample of 10 lamps will have a mean life less than 4950 hours?

is the answer .3632?

jim_thompson5910 · Answer

you're close, but I'm getting 0.3627

jim_thompson5910 · Answer

http://www.wolframalpha.com/input/?i=normal+cdf&a=*MC.normal+cdf-_*Formula.dflt-&f2=4950&f=NormalProbabilities.z_4950&f3=5000&f=NormalProbabilities.mu_5000&f4=450%2Fsqrt(10)&f=NormalProbabilities.sigma_450%2Fsqrt(10)&a=*FVarOpt.1-_***NormalProbabilities.z--.***NormalProbabilities.pr--.**NormalProbabilities.l-.*NormalProbabilities.r---.**NormalProbabilities.mu-.*NormalProbabilities.sigma--- sorry the link is long, you may have to copy/paste it into the address bar

anonymous · Answer

which is essentially the same thing

jim_thompson5910 · Answer

yeah it's close

anonymous · Answer

all i care about is the fact that i attempted it correctly...the steps.

jim_thompson5910 · Answer

well you basically will use the formula

z = (x - mu)/(sigma/sqrt(n))

to get the z-score

jim_thompson5910 · Answer

then use a calculator or a z-table

anonymous · Answer

i got you. thanks!

jim_thompson5910 · Answer

you're welcome