Do nice guys really finish last in business? Refer to the Nature (March 20, 2008) study of whether “nice guys finish last” in business, Exercise 11.18 (p. 653). Recall that college students repeatedly played a version of the game “prisoner’s dilemma,” where competitors choose cooperation, defection, or costly punishment. At the conclusion of the games, the researchers recorded the average payoff and the number of times punishment was used for each player. Based on a scatter plot of the data, the simple linear regression relating average payoff (y) to punishment use (x) resulted in SSE = 1.04.

a. Assuming a sample size of n = 28, compute the estimated standard deviation of the error distribution, s.

b. Give a practical interpretation of s.

Short Answer

Expert verified
  1. The estimated standard deviation of the error distribution is 0.2.
  2. It is preferable if it is small.

Step by step solution

01

Introduction

The standard error shows how far the population mean is expected to deviate from the sample mean. It indicates how much the sample mean will change if the research is repeated with new samples from the same population.

02

Finding s

s=SSEn-2=1.0428-2=1.0426=0.04=0.2

Therefore, the standard deviation of the error distribution s is 0.2.

03

Providing a practical interpretation of s 

“s” is a measure of the predicted value's variability around the regression line. It is preferable if it is small.

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Most popular questions from this chapter

Motivation and right-oriented bias. Evolutionary theory suggests that motivated decision makers tend to exhibit a right-oriented bias. (For example, if presented with two equally valued detergent brands on a supermarket shelf, consumers are more likely to choose the brand on the right.) In Psychological Science (November 2011), researchers tested this theory using data on all penalty shots attempted in World Cup soccer matches (totaling 204 penalty shots). The researchers believed that goalkeepers, motivated to make a penalty-shot save but with little time to make a decision, would tend to dive to the right. The results of the study (percentages of dives to the left, middle, or right) are provided in the table. Note that the percentages in each row corresponding to a particular match situation add to 100%. Use graphs to illustrate the distribution of dives for the three-match situations. What inferences can you draw from the graphs?

Source: Based on M. Roskes et al., "The Right Side? Under Time Pressure, Approach Motivation Leads to Right-Oriented Bias," Psychological Science, Vol. 22, No. 11, November 2011 (adapted from Figure 2)11

Congress voting on women’s issues. The American Economic Review (March 2008) published research on how the gender mix of a U.S. legislator’s children can influence the legislator’s votes in Congress. The American Association of University Women (AAUW) uses voting records of each member of Congress to compute an AAUW score, where higher scores indicate more favorable voting for women’s rights. The researcher wants to use the number of daughters a legislator has to predict the legislator’s AAUW score.

a. In this study, identify the dependent and independent variables.

b. Explain why a probabilistic model is more appropriate than a deterministic model.

c. Write the equation of the straight-line, probabilistic model.

Joint Strike Fighter program. Refer to the Air & Space Power Journal (March-April 2014) study of the Joint Strike Fighter program, Exercise 11.22 (p. 655). You fit the simple linear regression model relating y = estimated annual cost to x = year of initial aircraft operation.

a. Find s, the estimated standard deviation of the random error term, for the model.

b. Give a practical interpretation of s.

Stability of compounds in new drugs. Testing the metabolic stability of compounds used in drugs is the cornerstone of new drug discovery. Two important values computed from the testing phase are the fraction of compound unbound to plasma (fup) and the fraction of compound unbound to microsomes (fumic). A key formula for assessing stability assumes that the fup/fumic ratio is 1. Pharmacologists at Pfizer Global Research and Development investigated this phenomenon and reported the results in ACS Medicinal Chemistry Letters (Vol. 1, 2010). The fup/fumic ratio was determined for each of 416 drugs in the Pfizer database. An SPSS graph describing the fup/fumic ratios is shown below.

a. What type of graph is displayed?

b. What is the quantitative variable summarized in the graph?

c. Determine the proportion of fup/fumic ratios that fall above 1.

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The equation for a straight line (deterministic model) is

y=β0+β1x

If the line passes through the point (-2, 4), then x = -2, y = 4 must satisfy the equation; that is,

4=β0+β1(-2)

Similarly, if the line passes through the point (4, 6), then x = 4, y = 6 must satisfy the equation; that is,

6=β0+β1(4)

Use these two equations to solve for and ; then find the equation of the line that passes through the points (-2, 4) and (4, 6).

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