Question

A multiple-choice test contains 25 questions, each with 4 answers. Assume a student just guesses on each question. (a) What is the probability that the student answers more than 20 questions correctly

Answer 1

Answer:

9.68*10^-10

Step-by-step explanation:

The problem above can be solved using the binomial probability relation :

Where ;

P(x = x) = nCx * p^x * q^(n-x)

n = number of trials = 25

p = 1/4 = 0.25

q = 1 - p = 0.75

x = 20

P(x > 20) = p(x = 21) + p(x = 22) +.. + p(x = 25)

Using the binomial probability calculator to save computation time :

P(x > 20) = 9.68*10^-10