TEAS 7 Scientific Reasoning Practice Test

Random assignment ensures each participant has the same chance of ending up in any group, which helps create comparable groups at the start of an experiment. By giving everyone an equal opportunity for assignment—think of a coin flip, a random number, or a shuffled list—you minimize selection bias and other preexisting differences that could influence outcomes. If groups start out similar, any differences observed after the intervention are more likely due to the treatment itself rather than who happened to be in each group. Blinding, on the other hand, hides group membership from participants to reduce expectancy or reporting biases, but it doesn’t affect how participants are assigned. Double-blinding extends this concealment to researchers collecting outcomes. Stratification involves dividing participants into subgroups based on certain characteristics and then randomizing within those subgroups to ensure balanced representation across groups; it helps balance known factors but is not the mechanism that guarantees equal assignment probabilities across the entire sample.