30% of a city\'s habitants have at least 1 computer at home.250 people are surve

Question

30% of a city's habitants have at least 1 computer at home.250 people are surveyed in this city. 1.What is the probability that not more than 50 of thesurveyed have a computer at home. 2.What is the probability that between 45 and 80 of thesurveyed have a computer at home. 3.How many surveyed people have a computer at home? What isits standard deviation? 4.What is the probability that at leats 30 surveyed have acomputer at home. 30% of a city's habitants have at least 1 computer at home.250 people are surveyed in this city. 1.What is the probability that not more than 50 of thesurveyed have a computer at home. 2.What is the probability that between 45 and 80 of thesurveyed have a computer at home. 3.How many surveyed people have a computer at home? What isits standard deviation? 4.What is the probability that at leats 30 surveyed have acomputer at home.

Explanation / Answer

= E(X) =np = 250*0.3 = 75 (This is the average.)

= SD(X) = np(1-p) = (250*0.3*0.7) =7.246

z = (x – ) / = (50.5 – 75) / 7.246 =-3.38

P(X 50) = P(Z < -3.38) = 0.00036

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