Let X be a discrete random variable that denotes the number of junk e-mail messa
ID: 3253990 • Letter: L
Question
Let X be a discrete random variable that denotes the number of junk e-mail messages received in a day. A web site developer estimates that the probability function for X is: Answer the following questions, rounding your answers to two decimal places where appropriate. (a) What is the probability that the number of junk e-mail messages is less than or equal to 2, P(X lessthanorequalto 2)? (b) What is the probability that the number of junk e-mail messages is greater than 4? (c) What is the probability that at least one junk e-mail message will be received in a day?Explanation / Answer
a) P(X < 2)
= P(X = 0) + P(X = 1) + P(X = 2)
= 0.02 + 0.07 + 0.17
= 0.26
b) P(X > 4)
= P(X = 5) + P(X = 6)
= 0.18 + 0.25
= 0.43
c) P(X > 1)
= 1 - P(X < 1)
= 1 - P(X = 0)
= 1 - 0.02
= 0.98
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