In: Statistics and Probability
x | 0 | 1 | 2 | 3 | 4 |
P(X) | 0.45 | 0.3 | 0.2 | 0.04 | 0.01 |
(a) Find and interpret the expected value of X
(b)Find the variance of X
(c)Find the probability that a person has 1 sibling given that they have less than 3 siblings.
(d)Find the probability that a person has at least 1 sibling OR less than 2 siblings
Solution
x | P(x) | x * P(x) | x2 * P(x) |
0 | 0.45 | 0 | 0 |
1 | 0.3 | 0.3 | 0.3 |
2 | 0.2 | 0.4 | 0.8 |
3 | 0.04 | 0.12 | 0.36 |
4 | 0.01 | 0.04 | 0.16 |
1 | 0.86 | 1.62 |
a ) Mean = = X * P(X) = 0.86
b ) variance = 2 =X 2 * P(X) - 2
2 =1.62 - 0.7396
2=0.8804
2 = 0.93
c ) P ( x < 3 )
= P ( x = 0 ) + P ( x = 1 ) + P ( x = 2 )
= 0.45 +0.3 +0.2
= 0.95
probability= 0.95
d ) P ( x 2 )
= P ( x = 2 ) + P ( x = 3 ) + P ( x = 4)
= 0.2 +0.04 +0.01
= 0.25
probability= 0.25