Question

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...

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

Solutions

Expert Solution

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


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