A researcher wants to create and compare two groups in her study. She has the ch

Question

A researcher wants to create and compare two groups in her study. She has the choice of using ‘random assignment’ or ‘matching’. First, define ‘matching’. Second, describe how matching is different from ‘random assignment’, while defining random assignment. Finally, explain the problem with using ‘matching’ to create two groups for a study.

Consider a project designed to study UCM students. The researcher wants to use random assignment and random sampling to create two groups of UCM study volunteers. Use the above example to explain the difference between random assignment and random sampling. Which happens first, which happens second? Also, talk about external & internal validity, and specifically explain how random assignment / sampling are linked to each.

Explanation / Answer

Matching - A pair, or set of, matched samples are those in which each member of a sample is matched with a corresponding member in every other sample by reference to qualities other than those immediately under investigation. Matched samples are paired up so that the participants share every characteristic except for the one under investigation. The object of matching is to get better statistics by controlling for the effects of other unwanted variables.

Random Assignment - Random assignment is an aspect of experimental design in which study participants are assigned to the treatment or control group using a random procedure. The key word here is "random". Samples are not matched before to control for effects of other unwanted variables.

The problem with 'Matching' can be that even after careful matching of the pairs there will always be some variation. If there are too many factors of influence, the researcher can only hope to match the most influential variables, which is an approximation. In addition, the researcher might be incorrect in his assumptions about which variables are the most important and miss a major confounding variable.

Difference between random assignment and random sampling

Random sampling refers to how sample members are selected from the population for inclusion in the study. Random assignment is an aspect of experimental design in which study participants are assigned to the treatment or control group using a random procedure. Random sampling happens first and then random assignment. If Random sampling is done, results are generalizable. If Random Assignment is done, results infer causation.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.