# Help with finding the mean, variance and standard deviation

• Jul 18th 2007, 04:40 PM
mkcar
Help with finding the mean, variance and standard deviation
Hi, I can't seem to fiqure out how to find the standard deviation of this problem. I don't know how to get it, and where does it come from. The problem is this. n = 76, p =0.8. I know how to get the mean which is to take 76*0.8, then I'm lost. Could one of you smart people help me pleeze.
• Jul 18th 2007, 09:05 PM
CaptainBlack
Quote:

Originally Posted by mkcar
Hi, I can't seem to fiqure out how to find the standard deviation of this problem. I don't know how to get it, and where does it come from. The problem is this. n = 76, p =0.8. I know how to get the mean which is to take 76*0.8, then I'm lost. Could one of you smart people help me pleeze.

It would help if you state the problem clearly.

Presumably this is a question about the binomial distribution, with n trials with
a probability of success on each trial of p. Then the mean number of success
is np, and the standard deviation of the number of success is sqrt(np(1-p)).

RonL
• Jul 19th 2007, 08:28 AM
mkcar
I need to find the mean, variance and standard deviation of binomial distribution
Hi, the question is put down as this n = 76, p =0.8. I know how to find the mean, but finding the variance needs me to find the answer of the standard deviation. Thant is what is hard for me. thank you