Statistics
posted by Bill .
Use this information to calculate the mean and standard deviation of this random variable.
P(x) .25, .05, .55, .15

Find the mean first = sum of scores/number of scores
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
Standard deviation = square root of variance
I'll let you do the calculations.