Dr. Cortez determined that the mean level of depression for both experimental groups was the same. However, it is important to not only look at the central tendency of both groups, but also the or degree to which they differ from each other.

Variability

Explanation:

Variability is the trait that displays variation occurring in sample of experiment and results .Variation can be present in experiment as samples may differ, condition may differ,different measuring aspect, etc.

According to the question, variability is the factor that should be considered to determine degree of difference present between data and how they are separate from each other in terms of sample structure, measurement , rate, influence etc even though it is producing same results.

no , per capita income is not a true measure of the development because: -it only tells us about average income not how income is distributed among the people.it only give us an idea of the economic aspect.it is only at the qualitative basis.moreover, income is not only the way of development other factors are also as much as important as income.