probability distribution of a random variable

Question

Following is the probability distribution of a random variable that represents the number of extracurricular activities a college freshman participates in 

x	0	1	2	3	4
P(x)	0.06	0.14	0.45	0.21	0.14

 

a) Find the mean

b) Find the standard deviation. Round your answer to two decimal places.

c) Find the probability that a student participates in exactly two activities

  

d) Find the probability that a student participates in more than two activities

e) Find the probability that a student participates in at least one activity.

Answer 1

a) Mean is sum x(i)*P(x(i)), where i = 0, 1, 2, 3, 4

b) Std dev = [sum of x(i)^2*P(x(i))] - mean^2, where i = 0, 1, 2, 3, 4

c) 0.45

d) 0.21 + 0.14 = 0.35

e) 1 - P(x=0) = 1 -0.06 = 0.94