<PRE><B>Question 1104196</B>
use the binomial probability formula
:
Probability (P) ( k successes in n trials) = nCk * p^k * (1-p)^(n-k), where nCk = n! / (k! * (n - k)!)
:
for this problem p = 0.25 (probability of guessing a correct answer given 4 choices)
:
P ( 15 or more correct out of 20 ) = P (15 correct out of 20) + P (16 correct out of 20) + P (17 correct out of 20) + P (18 correct out of 20) + P (19 correct out of 20) + P (20 correct out of 20) = 3.8E06
:
P ( 5 or less correct out of 20 ) = P (5 correct out of 20) + P (4 correct out of 20) + P (3 correct out of 20) + P (2 correct out of 20) + P (1 correct out of 20) + P (0 correct out of 20) = 0.617 approximately 0.62
:
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