An exam consists of 40 multiple-choice questions. Each question has a choice of

Question

An exam consists of 40 multiple-choice questions. Each question has a choice of five answers, only one of which is correct. For each correct answer, a candidate gets 1 mark, and no penalty is applied for getting an incorrect answer. A particular candidate answers each question purely by guess-work. Using Normal approximation to Binomial distribution with continuity correction, what is the estimated probability this student obtains a score greater than or equal to 10? Please use R to obtain probabilities and keep at least 6 decimal places in intermediate steps. A. 0.3773 B. 0.7234 C. 0.2766 D. 0.1615 E. 0.5927

Explanation / Answer

let X is the marks obtained.

then X fololows normal with mean 40*0.2=8 and variance with 40*0.2*0.8=6.4,

so, probility (X>10 ) = pnorm(10, 8 ,sqrt(6.4))
[1] 0.7854023

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