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An Introduction to Simple Linear Regression - Assignment 6 | MATH 217, Assignments of Probability and Statistics

Material Type: Assignment; Class: Probability & Statistics; Subject: Mathematics; University: Indiana University of Pennsylvania-Main Campus; Term: Summer 2008;

Typology: Assignments

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Uploaded on 08/16/2009

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GSR 516 Summer 2008
Homework Assignment 6
Due July 29, 2008
Simple Linear Regression
"Women May Outrun Men, Researchers Suggest"
Women runners might start beating men in world-class competitions within a few
generations, researchers said Thursday.
An analysis of world records for a variety of distances found that women have been
improving about twice as quickly as men. And if that continues, the top female and male
runners might start performing equally well between the years 2015 and 2055 in the 200-,
400-, 800-, and 1,500-meter events, according to a study. The findings were reported in a
letter in the journal Nature.
"None of the current women's world-record holders at these events could even meet the
men's qualifying standard to compete in the 1992 Olympic games," researchers Brian
Wipp and Susan Ward wrote.
"However, it is the rates of improvement that are so strikingly different - the gap is
progressively closing." But other researchers said they doubted the projections because
they believed women's rate of improvement would slow.
Source: Journal staff and wire services, Milwaukee Journal, January 1992
Tasks
1. Construct a scatterplot of times in the 200-meters against year for the men's data.
Construct a separate scatterplot for the women's data. Describe the patterns in the
scatterplots. Specifically, are the patterns linear or at least approximately linear?
2. Calculate the correlation between men's times in the Olympic 200-meters and the
Olympic year. Do the same for the women's times. Which gender's times in the
Olympic 200-meters exhibit a stronger correlation with Olympic year?
3. Fit a least squares regression line to the data for men's times in the 200-meters.
Use technology or draw by hand the line on the men's scatterplot.
4. Fit a line to the data for women's times. Again, draw the line on the scatterplot.
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GSR 516 Summer 2008

Homework Assignment 6

Due July 29, 2008

Simple Linear Regression

"Women May Outrun Men, Researchers Suggest"

Women runners might start beating men in world-class competitions within a few

generations, researchers said Thursday.

An analysis of world records for a variety of distances found that women have been

improving about twice as quickly as men. And if that continues, the top female and male

runners might start performing equally well between the years 2015 and 2055 in the 200-,

400-, 800-, and 1,500-meter events, according to a study. The findings were reported in a

letter in the journal Nature.

"None of the current women's world-record holders at these events could even meet the

men's qualifying standard to compete in the 1992 Olympic games," researchers Brian

Wipp and Susan Ward wrote.

"However, it is the rates of improvement that are so strikingly different - the gap is

progressively closing." But other researchers said they doubted the projections because

they believed women's rate of improvement would slow.

Source: Journal staff and wire services, Milwaukee Journal , January 1992

Tasks

1. Construct a scatterplot of times in the 200-meters against year for the men's data.

Construct a separate scatterplot for the women's data. Describe the patterns in the

scatterplots. Specifically, are the patterns linear or at least approximately linear?

2. Calculate the correlation between men's times in the Olympic 200-meters and the

Olympic year. Do the same for the women's times. Which gender's times in the

Olympic 200-meters exhibit a stronger correlation with Olympic year?

3. Fit a least squares regression line to the data for men's times in the 200-meters.

Use technology or draw by hand the line on the men's scatterplot.

4. Fit a line to the data for women's times. Again, draw the line on the scatterplot.

5. Use the regression lines to make predictions for both men's and women's times in

the Olympic 200-meters in the Olympic years 2000, 2004, and 2008. Compute

residuals for the predictions you made for both men and women in 2000 and

2004. Why can’t you compute the residuals for your 2008 predictions?

6. At the Atlanta Olympics in 1996, Michael Johnson ran the 200-meters in 19.

seconds (wow!). Use the prediction you calculated for 1996 to compute Johnson's

residual.

Now compute the prediction for women in 1988, when Florence Griffith-Joyner

ran the 200-meters in 21.34 seconds. Calculate the residual for "Flo-Jo's" time.

Use the two residuals to reach a conclusion about which of the two times was

more "impressive" compared to the corresponding predictions. That is, which of

Michael Johnson's 1996 time and Florence Griffith-Joyner's 1998 time was farther

below what was predicted for that year?

7. Construct a graph displaying the data for both men and women as well as the

regression lines for men and women on the same plot.

8. Interpret the slopes of the regression lines for men and women in the context of

the problem. That is, what are the units of the slopes? Which slope is steeper?

9. Use the two regression lines you found to predict in what year men and women

will run the same times in the 200-meters. Do you think it is realistic to expect

that this will happen? Why or why not?

10. Write a letter to the editor of the Milwaukee Journal (the newspaper in which the

article at the beginning of this handout appeared) explaining your conclusion

about whether men and women will run the same times in the Olympic 200-

meters "between the years 2015 and 2055" as the article states might happen.

Note: You should not actually mail your letter to the Milwaukee Journal! But

please write it as if you were going to mail it! Use language that an editor would

understand, but refer to the statistical results you found to support your position.

The data are contained in the accompanying table, and are also available on the Datasets

and Contexts page of our WebCT site.