Question

A retrospective study of 102 pairs of twins was performed. The twin pairs each had one male child and one female child. Their birth weights were studied to determine if the male twin was consistently heavier.

The difference in weights was calculated by subtracting the female weight (in ounces) from the male weight (in ounces):

d=xm−xfd=xm-xf

After looking at 102 pairs of twins, the study finds the 95% confidence interval for the mean difference of weights (in ounces) is:

-1.9 < μdμd < 2.9

Can we be reasonably sure that the male twins are heavier than the females?

• Yes
• No

Why or why not?

Answer 1

Since , the difference in weights is calculated by,

Here , we want to test the hypothesis ,

Hypothesis : VS

Since , the 95% confidence interval for the mean difference of weights is ( -1.9 , 2.9 )

Here , the value lies in the 95% confidence interval.

Therefore , fail to reject Ho

Hence , we can not reasonably sure that the male twins are heavier than the females.