As part of their strategy to keep computer viruses in check, a company randomly
ID: 3133594 • Letter: A
Question
As part of their strategy to keep computer viruses in check, a company randomly selects 20% of its computers to have their hard drives (HDDs) get a weekly virus scan. 50 drives exist in the marketing department of the company.
a. What is the probability that more than 6 HDDs in marketing get scanned?
b. What is the probability that 3 or less HDDs in marketing get scanned?
c. On average, what is the number of HDDs that get scanned in marketing?
d. What is the variance in the number of HDDs that get scanned weekly in marketing?
e. What is the probability that all 20 HDDs in marketing get scanned?
Explanation / Answer
As part of their strategy to keep computer viruses in check, a company randomly selects 20% of its computers to have their hard drives (HDDs) get a weekly virus scan. 50 drives exist in the marketing department of the company.
a. What is the probability that more than 6 HDDs in marketing get scanned?
n=50
P=0.2
Binomial distribution used.
P(X=x) = (nCx) px (1-p)n-x
P( x >6) = 0.8966
b. What is the probability that 3 or less HDDs in marketing get scanned?
P( x 3) = 0.0057
c. On average, what is the number of HDDs that get scanned in marketing?
Expectation = np =50*0.2 = 10
d. What is the variance in the number of HDDs that get scanned weekly in marketing?
Variance = np(1 - p) = 8
e. What is the probability that all 20 HDDs in marketing get scanned?
P( x=20) = 0.0006
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