Question

1. Assume X has the following probability distribution :

X         1       2       3       4

P(X)    .1      .5      .2      .2

Compute the standard deviation of X.

Answer: .9219

How can I compute the answers to these types of questions in Excel?

Answer 1

Solution:

x	P(x)	x * P(x)	x2 * P(x)
1	0.1	0.1	0.1
2	0.5	1	2
3	0.2	0.6	1.8
4	0.2	0.8	3.2
Sum	1	2.5	7.1

Mean = X * P(X)

= 2.5

Standard deviation =

=X 2 * P(X) - 2

=  7.1 - (2.5)2 = 0.85

Standard deviation = = 0.9219