Using the binomial distribution, it is found that there is a 0.6836 = 68.36% probability that she guesses at least one right.
For each question, there are only two possible outcomes, either she gets it right or she does not get it right. The probability of getting a question right is independent of any other question, hence the <em>binomial distribution</em> is used to solve this question.
<h3>What is the binomial distribution formula?</h3>
The formula is:


The parameters are:
- x is the number of successes.
- n is the number of trials.
- p is the probability of a success on a single trial.
In this problem:
- There are 5 questions, hence n = 5.
- For each question, she guesses one out of 4 options, hence p = 1/4 = 0.25.
The probability that she guesses at least one right is:

In which:


Hence:

0.6836 = 68.36% probability that she guesses at least one right.
You can learn more about the binomial distribution at brainly.com/question/24863377
81 because each person has 9 people to greet and there’s 9 people so 9x9=81
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Answer: the population has a mean of less than 30
Explanation:
In interval estimation, the t distribution is applicable only when a. the population has a mean of less than 30. the sample standard deviation (s) is given instead of the population standard deviation