Explain, in your own words, the difference between random assignment and random sampling. Can one study make use of both random assignment and random sampling? If so, explain what that would look like. If not, explain why not. Discuss the difference in the conclusions that can be drawn depending on whether random assignment or random sampling is used
The Correct Answer and Explanation is:
Correct Answer:
Yes, a study can make use of both random sampling and random assignment, and they serve different but complementary purposes. Random sampling refers to how participants are chosen from the population, while random assignment refers to how participants are placed into different groups within the study.
Explanation
Random sampling and random assignment are two distinct methods used in research design, each serving a different goal. Random sampling is the process by which researchers select individuals from a larger population in such a way that every member of the population has an equal chance of being included in the sample. This technique enhances external validity, or the extent to which the results of the study can be generalized to the broader population.
On the other hand, random assignment occurs after the sample has been selected. It involves placing participants into different treatment or control groups purely by chance. This process ensures that each participant has an equal likelihood of being assigned to any given group, which improves internal validity, or the confidence with which researchers can conclude that the observed effects are due to the manipulation of the independent variable, and not due to pre-existing differences among participants.
A study can use both random sampling and random assignment. For example, suppose a researcher wants to test a new teaching method. They first randomly sample 100 students from a school district (ensuring the sample reflects the general student population). Then, they randomly assign those 100 students into two groups: one experiencing the new method and the other using the standard method. This design allows researchers to draw causal conclusions from the experiment (thanks to random assignment) and to generalize the findings to the broader population (thanks to random sampling).
In summary, random sampling helps generalize findings, while random assignment supports cause-and-effect conclusions. Using both strengthens a study’s overall validity.
