Data from two groups
When data are collected from two groups, we are usually interested in differences between the groups in general. The specific individuals are of less interest. Questions are therefore about the characteristics of the populations or processes that we assume underlie the data.
Example
The questions do not refer to the 16 specific subjects — they ask about whether anticipation of hypnosis affects the ventilation rate in general. We would like to use the answers to predict what will happen to other people.