Question 928115: its is noted that 8% of school students are left handed. If 20 students are randomly selected, calculate the
(a) probability that none of them are left handed
(b) probability that at most 2 are left handed
(c) mean and standard deviation for the number of left handed students
Answer by ewatrrr(24785)   (Show Source):
You can put this solution on YOUR website! p(left-handed) = .08, n = 20
Using a TI calculator 0r similarly a Casio fx-115 ES plus
P(x = 0LH) = binompdf(20, .08, 0)= .1887 0r = .92^20
P(x ≤ 2LH) = binomcdf(20, .08, 2)= .7879
mean = 1.6 s = sqrt(1.6*.92) = 1.2133
Re TY
Not quite sure what You mean by 'count'
P(x ≤ 2LH) = P(0) + P(1) + P(2) = .92^20 + (20C1).08^1(.92)^19 + 20C2(.08)^2(.92)^18
..........
mean(or expected value) = .08*20 = 1.6
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