Based on a study of 2,256 children between the ages of one and four, researchers at the Medical College of Wisconsin concluded that there was an association between iron deficiency and the length of time that a child is bottle-fed.

What is the population of interest? The 2,256 children that were in the study.

All children in the US.

The researchers at the Medical College of Wisconsin.

All children aged between the ages of one and four.

All children who were bottle-fed.

What group constitutes the sample? The 2,256 children that were in the study.

All children in the US.

The researchers at the Medical College of Wisconsin.

All children aged between the ages of one and four.

All children who were bottle-fed.