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To introduce her class to binomial distributions, Mrs. Desai gives a 10 -item, multiple-choice quiz. The catch is, that students must simply guess an answer (A through E) for each question. Mrs. Desai uses her computer's random number generator to produce the answer key so that each possible answer has an equal chance to be chosen. Patti is one of the students in this class. Let X=the number of Patti's correct guesses.

1. Show that Xis a binomial random variable.

Short Answer

Expert verified

It has been shown thatXis a binomial random variable.

Step by step solution

01

Given Information 

Mr. Desai gives =10times

X=The number of Patti's correct guesses.

02

Explanation

The algorithm chose correct responses at random, thus one trial should not alter the outcome of the others.

There were ten questions in total.

Each trial has a0.20 chance of succeeding.

As a result, this is a binomial situation.

Because it counts the number of successes, Xis a binomial random variable withn=10and p=0.20.

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Most popular questions from this chapter

Refer to the previous Check Your Understanding (page 390 ) about Mrs. Desai's special multiple-choice quiz on binomial distributions. We defined X=the number of Patti's correct guesses.

1. Find ฮผX. Interpret this value in context.

2. Find localid="1649452775386" ฯƒX. Interpret this value in context.

Ten lines in the table contain 400digits. The count of 0s in these lines is approximately Normal with

(a) mean 40; standard deviation 36.

(b) mean 40; standard deviation19.

(c) mean 40; standard deviation 6.

(d) mean 36; standard deviation6.

(e) mean 10; standard deviation 19.

Kids and toys Refer to Exercise 4. Calculate the mean of the random variable X and interpret this result in context.

Statistics for investing (3.2) Joe's retirement plan invests in stocks through an "index fund" that follows the behavior of the stock market as a whole, as measured by the Standard & Poor's (S&P) 500 stock index. Joe wants to buy a mutual fund that does not track the index closely. He reads that monthly returns from Fidelity Technology Fund have correlation r=0.77with the S&P500index and that Fidelity Real Estate Fund has correlation role="math" localid="1649424494964" r=0.37with the index.

(a) Which of these funds has the closer relationship to returns from the stock market as a whole? How do you know?

(b) Does the information given tell Joe anything about which fund has had higher returns?

A deck of cards contains 52cards, of which 4are aces. You are offered the following wager: Draw one card at random from the deck. You win \(10if the card drawn is an ace. Otherwise, you lose \)1. If you make this wager very many times, what will be the mean amount you win?

(a) About โˆ’\(1, because you will lose most of the time.

(b) About \)9, because you win \(10but lose only \)1.

(c) About โˆ’\(0.15; that is, on average you lose about 15cents. (d) About \)0.77; that is, on average you win about 77cents.

(e) About $0, because the random draw gives you a fair bet.

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