Question 1

In a study reported in the July 2007 issue of the Journal of Epidemiology and Community Health, researchers investigated whether veterans are more likely to commit suicide than nonveterans. They spent 12 years following 104,000 veterans who had served in the armed forces between 1917 and 1994, and compared them with 216,000 nonveterans. They found that 197 veterans and 311 nonveterans committed suicide.
-Identify the explanatory and response variables in this study.

Accepted Answer

The explanatory variable is whether a subject is a veteran or a nonveteran (a binary categorical variable). The response variable is whether the subject committed suicide (also a binary categorical variable).

Question 2

In a study reported in the July 2007 issue of the Journal of Epidemiology and Community Health, researchers investigated whether veterans are more likely to commit suicide than nonveterans. They spent 12 years following 104,000 veterans who had served in the armed forces between 1917 and 1994, and compared them with 216,000 nonveterans. They found that 197 veterans and 311 nonveterans committed suicide.
-Is this an experiment or an observational study? Explain briefly.

Accepted Answer

This is an observational study because the researchers did not determine who would/would not be a veteran.

Question 3

In a study reported in the July 2007 issue of the Journal of Epidemiology and Community Health, researchers investigated whether veterans are more likely to commit suicide than nonveterans. They spent 12 years following 104,000 veterans who had served in the armed forces between 1917 and 1994, and compared them with 216,000 nonveterans. They found that 197 veterans and 311 nonveterans committed suicide.
-Notice that more nonveterans than veterans committed suicide (311 vs. 197). Would you conclude that veterans are less likely to commit suicide than nonveterans? Explain.

Accepted Answer

No, you cannot conclude from this information that veterans are less likely to commit suicide than nonveterans. Because the sample sizes differed, you need to consider the suicide rates, not simply the counts. The suicide rate for veterans is $197 / 104,000$ or .001894 , whereas the suicide rate for nonveterans is $311 / 216,000$ or .00144 .

Question 4

In a study reported in the July 2007 issue of the Journal of Epidemiology and Community Health, researchers investigated whether veterans are more likely to commit suicide than nonveterans. They spent 12 years following 104,000 veterans who had served in the armed forces between 1917 and 1994, and compared them with 216,000 nonveterans. They found that 197 veterans and 311 nonveterans committed suicide.
-Calculate the relative risk of committing suicide, comparing veterans to nonveterans.

Accepted Answer

The answer of In a study reported in the July...

Question 5

In a study reported in the July 2007 issue of the Journal of Epidemiology and Community Health, researchers investigated whether veterans are more likely to commit suicide than nonveterans. They spent 12 years following 104,000 veterans who had served in the armed forces between 1917 and 1994, and compared them with 216,000 nonveterans. They found that 197 veterans and 311 nonveterans committed suicide.
-Describe and justify the conclusion that you would draw from this study.

Accepted Answer

The answer of In a study reported in the July...

Question 6

Is it better to praise a child's intelligence or effort? In a study reported in a 1998 issue of the Journal of Personality and Social Psychology, researchers investigated this question by randomly assigning fifthgraders into three groups. One group received praise for their intelligence after working on a set of problems; another group received praise for their effort; and a third (control) group received general praise that did not mention a specific attribute. Each child was then asked to write a description of the problems for a child in another state, including how many he or she solved correctly. One response variable was whether the child lied about how many problems he/she had solved correctly. The data are organized in the following table: 
-Analyze these data to investigate whether they suggest any relationship between the type of praise given to a child and the child's propensity for lying about performance. Write a paragraph describing your findings, and support your findings with a graphical display and calculations.

Accepted Answer

The answer of Is it better to praise a child's...

Question 7

The following side-by-side stemplot displays the total number of points scored per Super Bowl football game for the first 41 Super Bowls (from 1967-2007), separated according to the first 20 games (19671986) and the next 21 games (1987-2007): 
-Does this stemplot enable you to determine how many points were scored in the first Super Bowl? If so, what is this number?

Accepted Answer

The answer of The following side-by-side stemplot displays the total...

Question 8

The following side-by-side stemplot displays the total number of points scored per Super Bowl football game for the first 41 Super Bowls (from 1967-2007), separated according to the first 20 games (19671986) and the next 21 games (1987-2007): 
-Does this stemplot enable you to determine how many of the first 41 Super Bowls had a total of 37 points? If so, what is this number?

Accepted Answer

The answer of The following side-by-side stemplot displays the total...

Question 9

The following side-by-side stemplot displays the total number of points scored per Super Bowl football game for the first 41 Super Bowls (from 1967-2007), separated according to the first 20 games (19671986) and the next 21 games (1987-2007): 
-Does this stemplot provide evidence that Super Bowl games have become more high-scoring over time, more low-scoring over time, or neither? Explain.

Accepted Answer

The answer of The following side-by-side stemplot displays the total...

Question 10

The following side-by-side stemplot displays the total number of points scored per Super Bowl football game for the first 41 Super Bowls (from 1967-2007), separated according to the first 20 games (19671986) and the next 21 games (1987-2007): 
-The five lowest-scoring Super Bowls were all played among the first 20 games.

Accepted Answer

The early Super Bowls were generally lower-scoring due to different playing styles and strategies compared to modern games.

Question 11

The following side-by-side stemplot displays the total number of points scored per Super Bowl football game for the first 41 Super Bowls (from 1967-2007), separated according to the first 20 games (19671986) and the next 21 games (1987-2007): 
-The five highest-scoring Super Bowls were all played among the next 21 games.

Accepted Answer

The statement is incorrect because the five highest-scoring Super Bowls were not all played within the next 21 games. Super Bowl scores vary each year and are not necessarily concentrated in a specific range of games.

Question 12

The following histogram displays the magnitudes of the 614 earthquakes with Richter scale magnitude greater than 1.0 that occurred in the United States between March 25 and April 1, 2004: 
-Describe the shape of this distribution.

Accepted Answer