statistics
posted by cm .
according to data from the american medical association, 10% of us are left handed. If three people, are randomly selected find the probability that they are all left handed. If groups of 50 people are randomly selected, what is the mean and stadard deviation of left handed people.

For the first part:
You can use a binomial probability table, or calculate by hand using the following formula: P(x) = (nCx)(p^x)[q^(nx)]
For the second part:
Use the binomial approximation to a normal distribution.
mean = np = 50 * .10 = ?
standard deviation = √npq = (√(50 * .10 * .90) = ?
Note: q = 1  p
Finish the calculation.
I hope these few hints will help.