The batteries produced in a manufacturing plant have a mean time to failure of 30 months, with a standard deviation of 2 months.
1 answer:
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Answer:
0.0545 = 5.45% probability that exactly seven are retired people.
Step-by-step explanation:
For each stock investor, there are only two possible outcomes. Either they are retired people, or they are not. Stock investors are independent. This means that 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% of all stock investors are retired people.
This means that
a. What is the probability that exactly seven are retired people?
0.0545 = 5.45% probability that exactly seven are retired people.