SOLUTION: if 1% of all calculators are defective, find the mean, variance and standard deviation of a lot of 500 calculators. this site NEVER helps me. i found a similar problem alread

Algebra ->  Probability-and-statistics -> SOLUTION: if 1% of all calculators are defective, find the mean, variance and standard deviation of a lot of 500 calculators. this site NEVER helps me. i found a similar problem alread      Log On


   

Question 627092: if 1% of all calculators are defective, find the mean, variance and standard deviation of a lot of 500 calculators.
this site NEVER helps me. i found a similar problem already posted but the answer solution makes NO SENSE to me since they do not show or explain any of the steps. i think this site should be taken down unless people give detailed answers because seeing a bunch of fdjsigadfh equations is not helping me at all for statistics... with that said, any help is appreciated. heh
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Mean:

mu = np

mu = 500*0.01

mu = 5

So the mean is 5

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Variance:

sigma^2 = np*(1-p)

sigma^2 = 500*0.01*(1-0.01)

sigma^2 = 4.95

So the variance is 4.95
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Standard Deviation:

sigma = sqrt(np*(1-p))

sigma = sqrt(500*0.01*(1-0.01))

sigma = 2.2248595

So the variance is roughly 2.2248595

Note: the standard deviation is the square root of the variance.