Random Sampling and Assignment: Importance in Statistical Research, Summaries of Statistics

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Random sampling vs. assignment

Statistics 101

Duke University

Mine C¸ etinkaya-Rundel

Learning objective(s):

Classify a study as observational if the researcher merely observes the data and as an experiment if treatments are imposed on subjects. Assess whether the study’s results can be generalized to the population based on whether or not random sampling is employed. Determine whether the study’s results suggest causation or association association based on whether or not random assignment is employed.

Why random sampling and assignment?

Random sampling allows us to obtain a sample representative of the population. Therefore, results of the study can be generalized to the population. Random assignment allows us to make sure that the only difference between the various treatment groups is what we are studying. For example, in the serif/sans serif example, random assignment helps us create treatment groups that are similar to each other, and the only difference between them is that one group reads text in serif font and the other in sans serif font. Therefore, causality can be inferred.

Summary