Can you explain to me why we can be reasonably sure that male twins are heavier than the females? How am I supposed to really look at this? Thank you.

A retrospective study of 186 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 186 pairs of twins, the study finds the 90% confidence interval for the mean difference of weights (in ounces) is:

-1.1

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

• Yes
• No

Why or why not?