for a group of four men , the probability distribution for the number x who live through the next year is as given in the accompanying table. Find out the mean and the standard deviation
x | p(x)
0 | 0.05
1 | 0.15
2 | 0.45
3 | 0.25
4 | 0.10

Mean is found by applying


\mu = \sum_{i=1} ^N p_i x_i


The standard deviation is found from:


\sigma = \sqrt{ \sum_{i=1} ^N p_i (x_i -\mu)^2}


Take a shot at this and post back what you get.