Question

The following table denotes the probability distribution for a discrete random variable X.

x	-2	0	1	2	9
p(x)	0.1	0.3	0.2	0.3	0.1

The standard deviation of X is closest to

Group of answer choices

3.74

4.18

2.77

7.65

11

Answer 1

Solution

x	P(x)	x * P(x)	x2 * P(x)
-2	0.1	-0.2	0.4
0	0.3	0	0
1	0.2	0.2	0.2
2	0.3	0.6	1.2
9	0.1	0.9	8.1
	1	1.5	9.9

Standard deviation = =X 2 * P(X) - 2  

   =9.9 -2.25

=7.65

= 2.766

Standard deviation =2.77

Option 2.77 is correct.