Assistance for AMU MATH 120 Intro to statistics quiz 4 answers week 4 American Military University is available at Domyclass

Table of Contents

#### MATH 120 AMU QUIZ 4 question 1

Which of the following are continuous variables, and which are discrete?

(a) number of traffic fatalities per year in the state of Florida

continuous

discrete

(b) distance a golf ball travels after being hit with a driver

continuous

discrete

.

(c) time required to drive from home to college on any given day

continuous

discrete

(d) number of ships in Pearl Harbor on any given day

continuous

discrete

(e) your weight before breakfast each morning

continuous

discrete

#### MATH 120 AMU QUIZ 4 question 2

Consider the probability distribution shown below.

x 0 1 2

P(x) 0.05 0.30 0.65

Compute the expected value of the distribution. (Enter a number.)

Compute the standard deviation of the distribution. (Enter a number. Round your answer to four decimal places.)

#### MATH 120 AMU QUIZ 4 question 3

What is the income distribution of super shoppers? A supermarket super shopper is defined as a shopper for whom at least 70% of the items purchased were on sale or purchased with a coupon. In the following table, income units are in thousands of dollars, and each interval goes up to but does not include the given high value. The midpoints are given to the nearest thousand dollars.

Income range 5-15 15-25 25-35 35-45 45-55 55 or more

Midpoint x 10 20 30 40 50 60

Percent of super shoppers 20% 14% 22% 17% 19% 8%

(a) Using the income midpoints x and the percent of super shoppers, do we have a valid probability distribution? Explain.

Yes. The events are indistinct and the probabilities sum to less than 1.

Yes. The events are distinct and the probabilities sum to 1.

No. The events are indistinct and the probabilities sum to more than 1.

Yes. The events are distinct and the probabilities do not sum to 1.

No. The events are indistinct and the probabilities sum to 1.

(b) Use a histogram to graph the probability distribution of part (a). (Select the correct graph.)

A histogram with 6 bars is given. The horizontal axis is labeled: Income. The vertical axis is labeled: % Supr Shpprs. The leftmost bar is centered on the value 10 and is 20 units tall. Moving to the right, the second bar is centered on the value 20 and is 14 units tall. The third bar is centered on the value 30 and is 22 units tall. The fourth bar is centered on the value 40 and is 17 units tall. The fifth bar is centered on the value 50 and is 19 units tall. The sixth bar is centered on the value 60 and is 8 units tall.

A histogram with 6 bars is given. The horizontal axis is labeled: Income. The vertical axis is labeled: % Supr Shpprs. The leftmost bar is centered on the value 10 and is 22 units tall. Moving to the right, the second bar is centered on the value 20 and is 20 units tall. The third bar is centered on the value 30 and is 17 units tall. The fourth bar is centered on the value 40 and is 14 units tall. The fifth bar is centered on the value 50 and is 8 units tall. The sixth bar is centered on the value 60 and is 19 units tall.

A histogram with 6 bars is given. The horizontal axis is labeled: Income. The vertical axis is labeled: % Supr Shpprs. The leftmost bar is centered on the value 10 and is 19 units tall. Moving to the right, the second bar is centered on the value 20 and is 22 units tall. The third bar is centered on the value 30 and is 20 units tall. The fourth bar is centered on the value 40 and is 8 units tall. The fifth bar is centered on the value 50 and is 17 units tall. The sixth bar is centered on the value 60 and is 14 units tall.

A histogram with 6 bars is given. The horizontal axis is labeled: Income. The vertical axis is labeled: % Supr Shpprs. The leftmost bar is centered on the value 10 and is 8 units tall. Moving to the right, the second bar is centered on the value 20 and is 19 units tall. The third bar is centered on the value 30 and is 17 units tall. The fourth bar is centered on the value 40 and is 22 units tall. The fifth bar is centered on the value 50 and is 14 units tall. The sixth bar is centered on the value 60 and is 20 units tall.

(c) Compute the expected income μ of a super shopper (in thousands of dollars). (Enter a number. Round your answer to two decimal places.)

μ =

thousands of dollars

(d) Compute the standard deviation σ for the income of super shoppers (in thousands of dollars). (Enter a number. Round your answer to two decimal places.)

σ =

thousands of dollars

#### MATH 120 AMU QUIZ 4 question 4

A particular lake is known to be one of the best places to catch a certain type of fish. In this table, x = number of fish caught in a 6-hour period. The percentage data are the percentages of fishermen who caught x fish in a 6-hour period while fishing from shore.

x 0 1 2 3 4 or more

% 43% 35% 15% 6% 1%

(a) Convert the percentages to probabilities and make a histogram of the probability distribution. (Select the correct graph.)

A histogram with 5 bars is given. The horizontal axis is labeled: x. The vertical axis is labeled: P(x). The leftmost bar is centered on the value 0 and is 0.43 units tall. Moving to the right, the second bar is centered on the value 1 and is 0.06 units tall. The third bar is centered on the value 2 and is 0.15 units tall. The fourth bar is centered on the value 3 and is 0.35 units tall. The fifth bar is centered on the value 4, with the label “4 or more”, and is 0.01 units tall.

A histogram with 5 bars is given. The horizontal axis is labeled: x. The vertical axis is labeled: P(x). The leftmost bar is centered on the value 0 and is 0.43 units tall. Moving to the right, the second bar is centered on the value 1 and is 0.35 units tall. The third bar is centered on the value 2 and is 0.06 units tall. The fourth bar is centered on the value 3 and is 0.15 units tall. The fifth bar is centered on the value 4, with the label “4 or more”, and is 0.01 units tall.

A histogram with 5 bars is given. The horizontal axis is labeled: x. The vertical axis is labeled: P(x). The leftmost bar is centered on the value 0 and is 0.43 units tall. Moving to the right, the second bar is centered on the value 1 and is 0.15 units tall. The third bar is centered on the value 2 and is 0.35 units tall. The fourth bar is centered on the value 3 and is 0.06 units tall. The fifth bar is centered on the value 4, with the label “4 or more”, and is 0.01 units tall.

A histogram with 5 bars is given. The horizontal axis is labeled: x. The vertical axis is labeled: P(x). The leftmost bar is centered on the value 0 and is 0.43 units tall. Moving to the right, the second bar is centered on the value 1 and is 0.35 units tall. The third bar is centered on the value 2 and is 0.15 units tall. The fourth bar is centered on the value 3 and is 0.06 units tall. The fifth bar is centered on the value 4, with the label “4 or more”, and is 0.01 units tall.

(b) Find the probability that a fisherman selected at random fishing from shore catches one or more fish in a 6-hour period. (Enter a number. Round your answer to two decimal places.)

(c) Find the probability that a fisherman selected at random fishing from shore catches two or more fish in a 6-hour period. (Enter a number. Round your answer to two decimal places.)

(d) Compute μ, the expected value of the number of fish caught per fisherman in a 6-hour period (round 4 or more to 4). (Enter a number. Round your answer to two decimal places.)

μ =

fish

(e) Compute σ, the standard deviation of the number of fish caught per fisherman in a 6-hour period (round 4 or more to 4). (Enter a number. Round your answer to three decimal places.)

σ =

#### MATH 120 AMU QUIZ 4 question 5

Jim is a 60-year-old Anglo male in reasonably good health. He wants to take out a $50,000 term (i.e., straight death benefit) life insurance policy until he is 65. The policy will expire on his 65th birthday. The probability of death in a given year is provided.

x = age 60 61 62 63 64

P(death at this age) 0.01045 0.01324 0.01771 0.01993 0.02341

Jim is applying to Big Rock Insurance Company for his term insurance policy.

(a) What is the probability that Jim will die in his 60th year? (Enter a number. Enter your answer to five decimal places.)

Using this probability and the $50,000 death benefit, what is the expected cost to Big Rock Insurance (in dollars)? (Enter a number. Round your answer to two decimal places.)

$

(b) What is the expected cost to Big Rock Insurance for years 61, 62, 63, and 64 (in dollars)? (For each answer, enter a number. Round your answers to two decimal places.)

year 61 $

year 62 $

year 63 $

year 64 $

What would be the total expected cost to Big Rock Insurance over the years 60 through 64 (in dollars)? (Enter a number. Round your answer to two decimal places.)

$

(c) If Big Rock Insurance wants to make a profit of $700 above the expected total cost paid out for Jim’s death, how much should it charge for the policy (in dollars)? (Enter a number. Round your answer to two decimal places.)

$

(d) If Big Rock Insurance Company charges $5000 for the policy, how much profit does the company expect to make (in dollars)? (Enter a number. Round your answer to two decimal places.)

$

#### MATH 120 AMU QUIZ 4 question 6

Consider a binomial experiment with n = 9 trials where the probability of success on a single trial is p = 0.10. (For each answer, enter a number. Round your answers to three decimal places.)

(a) Find P(r = 0).

(b) Find P(r ≥ 1) by using the complement rule.

#### MATH 120 AMU QUIZ 4 question 7

Sociologists say that 95% of married women claim that their husband’s mother is the biggest bone of contention in their marriages (sex and money are lower-rated areas of contention). Suppose that ten married women are having coffee together one morning. Find the following probabilities. (For each answer, enter a number. Round your answers to three decimal places.)

(a) All of them dislike their mother-in-law.

(b) None of them dislike their mother-in-law.

(c) At least eight of them dislike their mother-in-law.

(d) No more than seven of them dislike their mother-in-law.

#### MATH 120 AMU QUIZ 4 question 8

Suppose approximately 75% of all marketing personnel are extroverts, whereas about 70% of all computer programmers are introverts. (For each answer, enter a number. Round your answers to three decimal places.)

(a) At a meeting of 15 marketing personnel, what is the probability that 10 or more are extroverts?

What is the probability that 5 or more are extroverts?

What is the probability that all are extroverts?

(b) In a group of 4 computer programmers, what is the probability that none are introverts?

What is the probability that 2 or more are introverts?

What is the probability that all are introverts?

#### MATH 120 AMU QUIZ 4 question 9

Consider a binomial distribution of 200 trials with expected value 80 and standard deviation of about 6.9. Use the criterion that it is unusual to have data values more than 2.5 standard deviations above the mean or 2.5 standard deviations below the mean to answer the following questions.

(a) Would it be unusual to have more than 120 successes out of 200 trials? Explain.

Yes. 120 is more than 2.5 standard deviations above the expected value.

Yes. 120 is more than 2.5 standard deviations below the expected value.

No. 120 is less than 2.5 standard deviations above the expected value.

No. 120 is less than 2.5 standard deviations below the expected value.

(b) Would it be unusual to have fewer than 40 successes out of 200 trials? Explain.

Yes. 40 is more than 2.5 standard deviations above the expected value.

Yes. 40 is more than 2.5 standard deviations below the expected value.

No. 40 is less than 2.5 standard deviations above the expected value.

No. 40 is less than 2.5 standard deviations below the expected value.

(c) Would it be unusual to have from 70 to 90 successes out of 200 trials? Explain.

No. 90 observations is more than 2.5 standard deviations above the expected value.

No. 70 to 90 observations is within 2.5 standard deviations of the expected value.

Yes. 70 to 90 observations is within 2.5 standard deviations of the expected value.

Yes. 70 observations is more than 2.5 standard deviations below the expected value.

#### MATH 120 AMU QUIZ 4 question 10

The quality-control inspector of a production plant will reject a batch of syringes if two or more defective syringes are found in a random sample of eight syringes taken from the batch. Suppose the batch contains 5% defective syringes.

(a) Make a histogram showing the probabilities of r = 0, 1, 2, 3, …, 7 and 8 defective syringes in a random sample of eight syringes. (Select the correct graph.)

A histogram with 7 visible bars is given. The horizontal axis is labeled: r. The vertical axis is labeled: P(r). The leftmost bar is centered on the value 0 and is approximately 0.17 units tall. Moving to the right, the second bar is centered on the value 1 and is approximately 0.34 units tall. The third bar is centered on the value 2 and is approximately 0.29 units tall. The fourth bar is centered on the value 3 and is approximately 0.15 units tall. The fifth bar is centered on the value 4 and is approximately 0.05 units tall. The sixth bar is centered on the value 5 and is approximately 0.01 units tall. The seventh bar is centered on the value 6 is very close to 0 units tall. The values 7, 8, are also labeled on the horizontal axis. There are no visible bars over these labels.

A histogram with 5 visible bars is given. The horizontal axis is labeled: r. The vertical axis is labeled: P(r). The leftmost bar is centered on the value 0 and is approximately 0.43 units tall. Moving to the right, the second bar is centered on the value 1 and is approximately 0.38 units tall. The third bar is centered on the value 2 and is approximately 0.15 units tall. The fourth bar is centered on the value 3 and is approximately 0.03 units tall. The fifth bar is centered on the value 4 and is approximately 0.01 units tall. The values 5, 6, 7, 8, are also labeled on the horizontal axis. There are no visible bars over these labels.

A histogram with 6 visible bars is given. The horizontal axis is labeled: r. The vertical axis is labeled: P(r). The leftmost bar is centered on the value 0 and is approximately 0.27 units tall. Moving to the right, the second bar is centered on the value 1 and is approximately 0.39 units tall. The third bar is centered on the value 2 and is approximately 0.24 units tall. The fourth bar is centered on the value 3 and is approximately 0.08 units tall. The fifth bar is centered on the value 4 and is approximately 0.02 units tall. The sixth bar is centered on the value 5 is very close to 0 units tall. The values 6, 7, 8, are also labeled on the horizontal axis. There are no visible bars over these labels.

A histogram with 4 visible bars is given. The horizontal axis is labeled: r. The vertical axis is labeled: P(r). The leftmost bar is centered on the value 0 and is approximately 0.66 units tall. Moving to the right, the second bar is centered on the value 1 and is approximately 0.28 units tall. The third bar is centered on the value 2 and is approximately 0.05 units tall. The fourth bar is centered on the value 3 and is approximately 0.01 units tall. The values 4, 5, 6, 7, 8, are also labeled on the horizontal axis. There are no visible bars over these labels.

(b) Find μ (in terms of the number of syringes). (Enter a number. Enter your answer to two decimal places.)

μ =

syringes

What is the expected number of defective syringes the inspector will find? (Enter a number. Enter your answer to two decimal places.)

syringes

(c) What is the probability that the batch will be accepted? (Enter a number. Round your answer to three decimal places.)

(d) Find σ (in terms of the number of syringes). (Enter a number. Round your answer to three decimal places.)

σ =

syringes

#### MATH 120 AMU QUIZ 4 question 11

Innocent until proven guilty? In Japanese criminal trials, about 95% of the defendants are found guilty. In the United States, about 60% of the defendants are found guilty in criminal trials. (Source: The Book of Risks, by Larry Laudan, John Wiley and Sons) Suppose you are a news reporter following nine criminal trials. (For each answer, enter a number.)

(a) If the trials were in Japan, what is the probability that all the defendants would be found guilty? (Round your answer to three decimal places.)

What is this probability if the trials were in the United States? (Round your answer to three decimal places.)

(b) Of the nine trials, what is the expected number of guilty verdicts in Japan? (Round your answer to two decimal places.)

verdicts

What is the expected number in the United Sates? (Round your answer to two decimal places.)

verdicts

What is the standard deviation in Japan? (Round your answer to two decimal places.)

verdicts

What is the standard deviation in the United States? (Round your answer to two decimal places.)

verdicts

#### MATH 120 AMU QUIZ 4 question 12

Use the geometric probability distribution to solve the following problem.

On the leeward side of the island of Oahu, in a small village, about 70% of the residents are of Hawaiian ancestry. Let n = 1, 2, 3, … represent the number of people you must meet until you encounter the first person of Hawaiian ancestry in the village.

(a) Write out a formula for the probability distribution of the random variable n. (Enter a mathematical expression.)

P(n) =

(b) Compute the probabilities that n = 1, n = 2, and n = 3. (For each answer, enter a number. Round your answers to three decimal places.)

P(1) =

P(2) =

P(3) =

(c) Compute the probability that n ≥ 4. Hint: P(n ≥ 4) = 1 − P(n = 1) − P(n = 2) − P(n = 3). (Enter a number. Round your answer to three decimal places.)

(d) What is the expected number of residents in the village you must meet before you encounter the first person of Hawaiian ancestry? Hint: Use μ for the geometric distribution and round. (Enter a number. Round your answer to the nearest whole number.)

residents