Krista has a quiz today. There are 4 questions with 4 options. Each question only has one correct answer. She wants to guess and get 3 out of the 4 questions right. What is the probability of her getting 3 right

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