Thousands of students apply for admission to graduate schools in economics each year with the intention of obtaining a PhD. The Southern Economic Journal (April 2008) published a guide to graduate study in economics by ranking the PhD programs at 129 colleges and universities. Each program was evaluated according to the number of publications published by faculty teaching in the PhD program and by the quality of the publications. Data obtained from the Social Science Citation Index (SSCI) were used to calculate an overall productivity score for each PhD program. The mean and standard deviation of these 129 productivity scores were then used to compute a z-score for each economics program. Harvard University had the highest z-score 1z = 5.082 and, hence, was the top-ranked school; Howard University was ranked last because it had the lowest z-score 1z = -0.812. The data (z-scores) for all 129 economic programs are saved in the data file.

a. Interpret the z-score for Harvard University.

b. Interpret the z-score for Howard University.

c. The authors of the Southern Economic Journal article note that “only 44 of the 129 schools have positive z-scores, indicating that the distribution of overall productivity is skewed to the right.” Do you agree?

Short Answer

Expert verified
  1. A total of 5.082 standard deviations are above the mean score.
  2. A total of 0.812 standard deviations are below the mean score.
  3. Yes.

Step by step solution

01

Interpretation of the z-score of Harvard University

The Southern Economic Journal has found the z-score associated with Harvard University is 5.082. This indicates that around 5.082 standard deviations are above the mean score of Harvard University.

02

Step 2:Interpretation of the z-score of Howard University

The Southern Economic Journal has found the z-score associated with Howard University is -0.812. This indicates that around 0.812 standard deviations are above the mean score of Harvard University.

03

Specification of skewness

The motion of the asseveration is correct that the distribution will be skewed to the right. It is because only a few schools have positive z-scores whereas a maximum number of schools have negative z-scores.

p+q=1q=1-p

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Most popular questions from this chapter

Do social robots walk or roll? A social (or service) robot is designed to entertain, educate, and care for human users. In a paper published by the International Conference on Social Robotics (Vol. 6414, 2010), design engineers investigated the trend in the design of social robots. Using a random sample of 106 social robots obtained through a Web search, the engineers found that 63 were built with legs only, 20 with wheels only, 8 with both legs and wheels, and 15 with neither legs nor wheels. This information is portrayed in the accompanying graph.

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U.S. business bankruptcies.The American Bankruptcy Institute and the National Bankruptcy Research Center monitor the number of business bankruptcy filings each quarter. The table below lists the number of business bankruptcy filings for each quarter of a recent 2-year period. FILING

a.Explain why the data in the table represent time series data.

b.Construct a time series plot for the quarterly number of bankruptcy filings.

c.Do you detect a trend in the time series plot? Explain.

Year

Quarter

Number of

Bankruptcies

2011

1

2

3

4

12,376

12,304

11,705

11,149

2012

1

2

3

4

10,998

10,374

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Question: Repair and replacement costs of water pipes.Pipes used in a water distribution network are susceptible to breakage due to a variety of factors. When pipes break, engineers must decide whether to repair or replace the broken pipe.

A team of civil engineers estimated the ratio of repair to replacement cost of commercial pipe based on the diameter (in millimeters) of the pipe. (IHS Journal of Hydraulic Engineering,September 2012.) Data for a sample of 13 different pipe sizes are provided in the table. Use a scatterplot to aid the engineers in detecting a trend in the data. Does it appear that the ratio of repair to replacement cost is strongly associated with pipe size?

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8.60

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Calculate the range, variance, and standard deviation for the following samples:

a.4, 2, 1, 0, 1

b.1, 6, 2, 2, 3, 0, 3

c.8, -2, 1, 3, 5, 4, 4, 1, 3, 3

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Active nuclear power plants.Refer to Exercise 2.54 (p. 98) and the Nuclear Energy Institute’s data on the number of nuclear power plants operating in each of 30 states.

a.Find the range, variance, and standard deviation of this data set.

b.Eliminate the largest value from the data set and repeat part a.What effect does dropping this measurement have on the measures of variation found in part a?

c.Eliminate the smallest and largest value from the data set and repeat part a. What effect does dropping both of these measurements have on the measures of variation found in part a?

State

Status

Number of Power Plants

Alabama

Regulated

2

Arizona

Regulated

1

Arkansas

Regulated

1

California

Regulated

1

Connecticut

Deregulated

1

Florida

Regulated

3

Georgia

Regulated

2

Illinois

Deregulated

6

Iowa

Deregulated

1

Kansas

Regulated

1

Louisiana

Regulated

2

Maryland

Deregulated

1

Massachusetts

Deregulated

1

Michigan

Deregulated

3

Minnesota

Regulated

2

Mississippi

Regulated

1

Missouri

Regulated

1

Nebraska

Regulated

2

New Hampshire

Deregulated

1

New Jersey

Deregulated

3

New York

Deregulated

4

North Carolina

Regulated

3

Ohio

Deregulated

2

Pennsylvania

Deregulated

5

South Carolina

Regulated

4

Tennessee

Regulated

2

Texas

Deregulated

2

Virginia

Regulated

2

Washington

Regulated

1

Wisconsin

Deregulated

1

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