a. W any individual question?orectly fo verage, how many questions would a stude

Question

a. W any individual question?orectly fo verage, how many questions would a student answer correctly for the entire test? What is the probability that a student would get c. than 12 answers correct simply by guessing more true/false test has 20 questions. If a student is simply guessing at the answers, a. On average, how many questions would a student b. What is the probability that a student would answer c. What is the probability that a student would answer correctly for the entire test? more than 15 questions correctly simply by guessing? answer fewer than 7 questions correctly simply by guessing?

Explanation / Answer

(a) p = 0.5, n = 20

= np = 20 * 0.5 = 10

(b) P(x > 15) = P(16) + P(17) + P(18) + P(19) + P(20)

= 20C16 0.5^16 0.5^4 + 20C17 0.5^17 0.5^3 + 20C18 0.5^18 0.5^2 + 20C19 0.5^19 0.5^1 + 20C20 0.5^20 0.5^0

= 0.0059

(c) P(x < 6) = P(0) + P(1) + ... + P(6)

= 30C0 0.5^0 0.5^20 + 20C1 0.5^1 0.5^19 + ... + 20C6 0.5^6 0.5^14

= 0.0577

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