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# Liberty BUSI 230 Week 5 Exercises 6.4-7.3 Answers Complete Solutions

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### Question 1

What is a population parameter?

A population parameter is a descriptive measure of a .

Give three examples. (Select all that apply.)

### Question 2

What is a sample statistic?

A descriptive measure of a .

Give three examples. (Select all that apply.)

### Question 3

List two unbiased estimators and their corresponding parameters. (Select all that apply.)

## STATUS

### Question 4

Suppose x has a distribution with a mean of 90 and a standard deviation of 36. Random samples of size n = 64 are drawn.

(a) Describe the x distribution and compute the mean and standard deviation of the distribution

x has distribution with mean μx = and standard deviation σx = .

(b) Find the z value corresponding to x = 99.

(c) Find P(x < 99). (Round your answer to four decimal places.)

P(x < 99) =

(d) Would it be unusual for a random sample of size 64 from the x distribution to have a sample mean less than 99? Explain.

### Question 5

Coal is carried from a mine in West Virginia to a power plant in New York in hopper cars on a long train. The automatic hopper car loader is set to put 56 tons of coal into each car. The actual weights of coal loaded into each car are normally distributed, with mean μ = 56 tons and standard deviation σ = 1.2 ton.

(a) What is the probability that one car chosen at random will have less than 55.5 tons of coal? (Round your answer to four decimal places.)

(b) What is the probability that 19 cars chosen at random will have a mean load weight x of less than 55.5 tons of coal? (Round your answer to four decimal places.)

(c) Suppose the weight of coal in one car was less than 55.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment?

Suppose the weight of coal in 19 cars selected at random had an average x of less than 55.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment? Why?

### Question 6

Let x be a random variable that represents white blood cell count per cubic milliliter of whole blood. Assume that x has a distribution that is approximately normal, with mean μ = 7600 and estimated standard deviation σ = 2550. A test result of x < 3500 is an indication of leukopenia. This indicates bone marrow depression that may be the result of a viral infection.

(a) What is the probability that, on a single test, x is less than 3500? (Round your answer to four decimal places.)

(b) Suppose a doctor uses the average x for two tests taken about a week apart. What can we say about the probability distribution of x?

What is the probability of x < 3500? (Round your answer to four decimal places.)

(c) Repeat part (b) for n = 3 tests taken a week apart. (Round your answer to four decimal places.)

(d) Compare your answers to parts (a), (b), and (c). How did the probabilities change as n increased?

If a person had x < 3500 based on three tests, what conclusion would you draw as a doctor or a nurse?