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A teacher gave a 5 question multiple choice

quiz. Each question had 4 choices to select
from. If the a student completely guessed
on every problem, what is the probability
that they will have less than 3 correct
answers? (CDF)

A)0.896
B)0.088
C)0.984
D)0.264

User Grandia
by
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1 Answer

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To solve this problem, we can use the binomial distribution formula:

P(X < 3) = P(X = 0) + P(X = 1) + P(X = 2)

where X is the number of correct answers, and P(X = k) is the probability of getting k correct answers out of 5 questions.

The probability of getting a single question correct by guessing is 1/4, and the probability of getting a single question incorrect is 3/4. Therefore, we can calculate P(X = k) using the binomial probability formula:

P(X = k) = (5 choose k) * (1/4)^k * (3/4)^(5-k)

where (5 choose k) is the binomial coefficient, which represents the number of ways to choose k items out of 5.

Plugging in k = 0, 1, and 2, we get:

P(X = 0) = (5 choose 0) * (1/4)^0 * (3/4)^5 = 243/1024
P(X = 1) = (5 choose 1) * (1/4)^1 * (3/4)^4 = 405/1024
P(X = 2) = (5 choose 2) * (1/4)^2 * (3/4)^3 = 270/1024

Adding these probabilities together, we get:

P(X < 3) = P(X = 0) + P(X = 1) + P(X = 2) = 918/1024

Simplifying this fraction, we get:

P(X < 3) = 459/512

Therefore, the answer is not one of the choices given.
User Brahmakumar M
by
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