a-team-of-researchers-is-investigating-the-impact-of-a-new-concentration-enhanci

Question

A team of researchers is investigating the impact of a new concentration-enhancing supplement on college students. A total of 4040 students aged 1818–2020 agree to participate. The students are randomly assigned to receive either the supplement or a placebo daily for two weeks. Their performance is assessed using standardized focus and attention tests at both the beginning and the end of the study. How could blocking be used in the design of this experiment to improve its accuracy?

Accepted Answer

Block by caffeine use; then randomly assign within each block.

Answer

Let students choose which group they want to join.

Answer

Assign students alphabetically to reduce bias.

Answer

Block by test scores after the study ends for better comparisons.