Answer:
The probability is 0.258
Step-by-step explanation:
In this question, we want to know the probability of Krista getting exactly 3 out of the options she chooses right.
For all the questions, there are 4 questions with 4 options each
Total number of options is 4 * 4 = 16 options
there are 3 wrong options and one correct option per question. Total number of correct option is 4 and the total number of wrong options is 12
Probability of selecting a wrong option is 12/16 = 3/4 while the probability of selecting a correct option is 1/4
Thus, we can use a Bernoulli approximation to get this probability of getting three right.
let the probability of selecting a correct option be p and that of a wrong option be a.
Probability of selecting exactly three correct ones will be;
P(r = 3) = nCr p^r q^(n-r)
where n is the total number of options and r is the number of options we are selecting to be correct.
The probability = 12C3 * (1/4)^3 * (3/4)^9
= 220 * 0.015625 * 0.075084686279 = 0.258
