# Statistical Techniques in Business & Economics by Lind

EXERCISES FROM LIND (Statistical Techniques in Business & Economics by Lind, et al)

1. The Grand Strand Family Medical Center is specifically set up to treat minor medical emergencies for visitors to the Myrtle Beach area. There are two facilities, one in the Little River Area and the other in Murrells Inlet. The Quality Assurance Department wishes to compare the mean waiting time for patients at the two locations. Samples of the waiting times, reported in minutes, follow:

Location Waiting Time

Little River 31.73 28.77 29.53 22.08 29.47 18.60 32.94 25.18 29.82 26.49

Murrells Inlet 22.93 23.92 26.92 27.20 26.44 25.62 30.61 29.44 23.09 23.10 26.69 22.31

At the .05 significance level, is there a difference in the mean waiting time?

3. A consumer buying cooperative tested the effective heating area of 20 different electric space heaters with different wattages. Here are the results.

Heater Wattage Area

1 1,500 205

2 750 70

3 1,500 199

4 1,250 151

5 1,250 181

6 1,250 217

7 1,000 94

8 2,000 298

9 1,000 135

10 1,500 211

11 1,250 116

12 500 72

13 500 82

14 1,500 206

15 2,000 245

16 1,500 219

17 750 63

18 1,500 200

19 1,250 151

20 500 44

a. Compute the correlation between the wattage and heating area. Is there a direct or an indirect relationship?

b. Conduct a test of hypothesis to determine if it is reasonable that the coefficient is greater than zero. Use the .05 significance level.

c. Develop the regression equation for effective heating based on wattage.

d. Which heater looks like the "best buy" based on the size of the residual?

3. The Banner Mattress and Furniture Company wishes to study the number of credit applications received per day for the last 300 days. The information is stated below:

Number of Credit Frequency

Applications (Number of Days)

0 50

1 77

2 81

3 48

4 31

5 or more 13

To interpret, there were 50 days on which no credit applications were received, 77 days on which only one application was received, and so on. Would it be reasonable to conclude that the population distribution is Poisson with a mean of 2.0? Use the .05 significance level. Hint: To find the expected frequencies use the Poisson distribution with a mean of 2.0. Find the probability of exactly one success given a Poisson distribution with a mean of 2.0. Multiply this probability by 300 to find the expected frequency for the number of days in which there was exactly one application. Determine the expected frequency for the other days in a similar manner.

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#### Solution Summary

Step by step answers for questions from Statistical Techniques in Business & Economics by Lind

Sampling, Central Limit Theorem and Confidence Intervals Discussion Questions

Exercise 1

From Chapter 7 of Lind, submit your responses to

problem #16 on pp. 237

The mean of a normal probability distribution is 400 pounds. The standard deviation is 10 pounds.

What is the area between 415 pounds and the mean of 400 pounds?

What is the area between the mean and 395 pounds?

What is the probability of selecting a value at random and discovering that it has a value of less than 395 pounds?

and problem #42 on pp. 248.

The accounting department at Weston Materials, Inc., a national manufacturer of unattached garages, reports that it takes two construction workers a mean of 32 hours and a standard deviation of 2 hours to erect the Red Barn model. Assume the assembly times follow the normal distribution.

Determine the z values for 29 and 34 hours. What percent of the garages take between 32 hours and 34 hours to erect?

What percent of the garages take between 29 hours and 34 hours to erect?

What percent of the garages take 28.7 hours or less to erect?

Of the garages, 5 percent take how many hours or more to erect?

Exercise 2

Review the multiple choice problems below and select the best choice.

2A: Management claims that the probability of a defective relay is only 0.001. The probability of the relay not being defective is:

a. 0.002

b. 0.000001

c. 0.999

d. 1.0

2B: A study of absenteeism from the classroom is being conducted. In terms of statistics, the study is called:

a. An experiment

b. An event

c. An outcome

d. A joint probability

2C: A normal probability distribution is

a. Symmetric around the mean

b. Bell shaped

c. Asymptotic to the X-axis

d. All of the above

2D: To apply this rule of addition, P(A or B or C) P(A) P(B) P(C), the events must be

a. Joint events

b. Conditional events

c. Mutually exclusive events

d. Independent events

2E: For a probability distribution, the sum of the probabilities for all possible outcomes must equal

a. 0.5

b. 1.0

c. 1.5

d. 0.0

Exercise 3

Read Lind Chapter 8 and then submit your response to the following problem:

Urban Plastic Products, Inc. is concerned about the inside diameter of the plastic PVC pipe it produces. A machine extrudes the pipe, which is then cut into 10-foot lengths. About 720 pipes are produced per machine during a two-hour period. How would you go about taking a sample from the two-hour production period?

Exercise 4

From Lind Chapter 9, respond to problem #32, #38 on printed page 319.

solve the attached problems

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