Question

A retrospective study of 154 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−xf

After looking at 154 pairs of twins, the study finds the 90% confidence interval for the mean difference of weights (in ounces) is:

0.7 < μdμd < 4.6

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

• Yes
• No

Why or why not?

Answer 1

After looking at 154 pairs of twins, the study finds the 90% confidence interval for the mean difference of weights (in ounces) is:

0.7 < μd < 4.6

In this kind of study

Null hypothesis: μd = 0 ( There is no significant difference among the weights of the male and female twins )

Alternate hypothesis : μd > 0 ( Male twins are slightly heavier than female twins )

The confidence interval does not contain the value 0

0.7 < μd < 4.6

Therefore, we can say that null hypothesis is rejected and alternate hypothesis is accepted

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

• Yes