Posted by Bill on Tuesday, March 26, 2013 at 8:02pm.
Use this information to calculate the mean and standard deviation of this random variable.
P(x) .25, .05, .55, .15

Statistics  PsyDAG, Wednesday, March 27, 2013 at 2:08pm
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.