Which term refers to the relation among subjects in a dependent sample?

The term that best describes the relation among subjects in a dependent sample is indeed matched or related characteristics. In a dependent sample, also known as a paired sample, the subjects in one group are related or match closely with subjects in another group. This relationship can stem from various factors, such as being paired based on pre-existing characteristics (like age, gender, or pre-test scores) or by being the same subjects measured at different times.

This methodological design allows researchers to control for individual differences, making it easier to identify the effect of the independent variable being tested. In essence, since the comparisons are made within related groups, the findings are often more robust and meaningful as they can effectively take into account the variation that exists within subjects themselves.

The incorrect options highlight different concepts in research methodology. Independent comparison suggests evaluating subjects as distinct and separate, which does not apply to dependent samples. Random assignment typically refers to allocating subjects randomly into groups to eliminate biases but is not directly relevant to the idea of dependence among subjects. Random selection of unrelated subjects clearly contrasts with the idea of having a dependent sample, which relies on relationships among subjects rather than unrelated ones.