4)
Solution
Given that ,
p = 0.2
1 - p = 0.8
n = 15
Using binomial probability formula ,
P(X = x) = (n C x) * px * (1 - p)n - x
P(X 4) = P(X < 4)
= P(X = 0) + P(X = 1) + P(X = 2) + P(X = 3)
= (15 C 0) * 0.20 * (0.8)15 + (15 C 1) * 0.21 * (0.8)14 + (15 C 3) * 0.23 * (0.8)13 + (15 C 3) * 0.23 * (0.8)12
= 0.3518
Probability = 0.3518
Expected number of questions = 15 * 0.2 = 3
(5 points) A multiple-choice examination has 15 questions, each with 5 possible answers only one ...
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