In: Statistics and Probability
Mimi plans to make a random guess at 5 true-or-false questions.
a. Assume random number X is the number of correct answers Mimi gets. As we know, X follows a binomial distribution. What is n (the number of trials), p (probability of success in each trial) and q (probability of failure in each trial)?
b. How many correct answers can she expect to get?
Mimi plans to make a random guess at a test containing 5 true-or-false questions.
a. Mimi plans to make a random guess at 5 true-or-false questions. What is the probability that Mimi will pass the test by random guess?
b. What function can be used to find the probability?
(a) Number of trials, n = 5
Probability of success in each trial, p = 0.5 (since any one option true or false can be correct both of which has probability of 0.5)
Probability of failure in each trial, q = 1 - p = 0.5
(b) Number of correct answers that she can expect to get = np = 2.5
Here, the criteria of passing the test is not given
(a)
Case 1: When all the answers need to be correct to pass the test, the probability of passing the test by random guess = = 1/32
Case 2: When atleast 4 out of 5 answers need to be correct, the required probability = = 6/32
Case 3: When atleast 3 out of 5 answers need to be correct, the required probability = = 1/2
Case 2: When atleast 2 out of 5 answers need to be correct, the required probability =
= 26/32
(b) Binomial distribution can be used
P(X = x) = , x = 0,1,2,....,n