Do left-handed people live shorter lives than right-handed people? A study of th

Question

Do left-handed people live shorter lives than right-handed people? A study of this question examined a sample of 949 death records and contacted next of kin to determine handedness. Note that there are many possible definitions of "left-handed." The researchers examined the effects of different definitions on the results of their analysis and found that their conclusions were not sensitive to the exact definition used. For the results presented here, people were defined to be right-handed if they wrote, drew, and threw a ball with the right hand. All others were defined to be left-handed. People were classified by gender (female or male) and handedness (left or right), and a 2 × 2 ANOVA was run with the age at death as the response variable. The F statistics were 22.36 (handedness), 37.44 (gender), and 2.10 (interaction). The following marginal mean ages at death (in years) were reported: 77.39 (females), 71.32 (males), 75.00 (right-handed), and 66.03 (left-handed).

(a) For each of the F statistics given, find the degrees of freedom and an approximate P-value. Summarize the results of these tests.
1

(b) Using the information given, write a short summary of the results of the study.
2

Explanation / Answer

Answer:

People were classified by gender (female or male) and handedness (left or right), and a 2 × 2 ANOVA was run with the age at death as the response variable. The F statistics were 22.36 (handedness), 37.44 (gender), and 2.10 (interaction). The following marginal mean ages at death (in years) were reported: 77.39 (females), 71.32 (males), 75.00 (right-handed), and 66.03 (left-handed).

(a) For each of the F statistics given, find the degrees of freedom and an approximate P-value. Summarize the results of these tests.

df

F

P value

handedness

1

22.36

0.0000

gender

1

37.44

0.0000

interaction

1

2.10

0.1476

error

945

Total

948

Using the information given, write a short summary of the results of the study.

The handedness effect is significant, F=22.36, P=0.0000 which is < 0.05 level.

The gender effect is significant, F=37.44, P=0.0000 which is < 0.05 level.

The interaction between handedness and gender effect is not significant, F=2.10, P=0.1476 which is > 0.05 level.

df

F

P value

handedness

1

22.36

0.0000

gender

1

37.44

0.0000

interaction

1

2.10

0.1476

error

945

Total

948

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