Answer:
D. Find the cumulative probability for 8 in a binomial distribution with n = 20 and p = 0.5.
Step-by-step explanation:
For each question, there are only two possible outcomes. Either the student guesses the correct answer, or he does not. The probability of the student is guessing the answer of a question correctly is independent of other questions. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
20 questions
This means that
How would you find the probability that the student will get 8 or fewer answers correct?
That is, it is the same as the cumulative probability for 8.
So the correct answer is:
D. Find the cumulative probability for 8 in a binomial distribution with n = 20 and p = 0.5.