1. Basic terminology

Psychologists conducted a study to determine the average age an infant starts to walk. A total of 56 infants who had not begun to walk were selected for the study. These infants were followed until they began to walk. Their ages at the onset of walking were recorded.

The individuals of interest in the study are .

The variable in the study is . This is a variable.

The data collected for this study are an example of data. Therefore, the average age at onset of walking in the study is a .