The random variable X, the number of people to revert to their first learned method under stress, has a binomial distribution with n = 40 and p = 0.2. Find the probability that at least eight of the 40 subjects revert to their first learned method. Round your answer to four decimal places.

0.5628 = 56.28% probability that at least eight of the 40 subjects revert to their first learned method.

Step-by-step explanation:

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.

In this problem we have that:

Find the probability that at least eight of the 40 subjects revert to their first learned method.

Either less than 8 do, or at least 8 do. The sum of the probabilities of these events is decimal 1. So

We want . So

In which

So

0.5628 = 56.28% probability that at least eight of the 40 subjects revert to their first learned method.

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step-by-step explanation: