What method helps ensure groups are similar at baseline in an intervention study?

What method helps ensure groups are similar at baseline in an intervention study?

• A. Randomization
• B. Blinding
• C. Stratified matching
• D. Cross-over design

Answer: (A)

Random assignment of participants to groups is the method that helps ensure groups are similar at the start of an intervention study. By giving everyone an equal chance to be in either group, known and unknown baseline differences tend to balance out, so observed outcomes are more likely due to the intervention rather than preexisting differences. This reduces selection bias and confounding, especially as sample size grows. While the other approaches address different concerns—blinding protects outcome assessment from bias, stratified matching can improve balance on specific characteristics but is more complex and limited to those variables, and a cross-over design uses the same participants for multiple treatments—random assignment remains the standard way to achieve comparable groups at baseline.

Random assignment of participants to groups is the method that helps ensure groups are similar at the start of an intervention study. By giving everyone an equal chance to be in either group, known and unknown baseline differences tend to balance out, so observed outcomes are more likely due to the intervention rather than preexisting differences. This reduces selection bias and confounding, especially as sample size grows. While the other approaches address different concerns—blinding protects outcome assessment from bias, stratified matching can improve balance on specific characteristics but is more complex and limited to those variables, and a cross-over design uses the same participants for multiple treatments—random assignment remains the standard way to achieve comparable groups at baseline.