Question

The number X of cars that Linda hopes to sell has the distribution:

Cars sold    0   1    2   3

Probability 0.2 0.1      0.3    0.4

Find the mean and standard deviation of X.

		1.9, 1.29
		0.25, 1.29
		1.9, 1.136
		0.25, 1.136

Answer 1

Solution:

x	P(x)	x * P(x)	x2 * P(x)
0	0.2	0	0
1	0.1	0.1	0.1
2	0.3	0.6	1.2
3	0.4	1.2	3.6
Sum	1	1.9	4.9

Mean = X * P(X)

= 1.9

Standard deviation =

=X 2 * P(X) - 2

=  4.9 - (1.9)2 = 1.29

Standard deviation = = 1.136

The mean and Standard deviation of X . 1.9 , 1.136