Answer:
Step-by-step explanation:
Given that a multiple choice test 30 questions, and each question has 5 answer choices (exactly one of which is correct).
When a student taking the test guesses randomly on all questions,p for success in each trial = 1/5 =0.2
As there are two outcomes and each event is independent of the other
X no of correct questions is binomial with n = 30 and p = 0.2
If approximated to normal
mean=np = 15 and Variance = np(1-p) = 4.8
Std dev = 2.191
X is normal (15, 2.191)
His expected value = mean = np
Required prob = P(X>15) = P(X>14.5) using continuity correction
=P(Z>-0.5/2.191) = P(Z>-0.23) =0.5910
