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 o

Question

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​

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Nevaeh 2 weeks 2021-09-11T21:11:12+00:00 1 Answer 0

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    2021-09-11T21:12:26+00:00

    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

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45:7+7-4:2-5:5*4+35:2 =? ( )