Which analysis assigns subjects to the groups they were randomized to?

Which analysis assigns subjects to the groups they were randomized to?

• A. Per-protocol Analysis
• B. Intention-to-treat Analysis
• C. As-treated Analysis
• D. Randomized-block Analysis

Answer: (B)

Intention-to-treat analysis assigns subjects to the groups to which they were randomized, regardless of whether they actually followed the assigned treatment, adhered to the protocol, or dropped out. This preserves the original randomization, so the comparison reflects the treatment strategy as it would be used in practice and avoids biases that come from excluding nonadherent participants or reclassifying them by the treatment they ended up receiving. Per-protocol analysis, for example, would analyze only those who followed the protocol, which can distort the treatment effect; as-treated analysis looks at the treatment actually received, which can introduce bias if reasons for switching are related to prognosis. Randomized-block refers to the way randomization was organized rather than how outcomes are analyzed, so it’s not about assigning to groups after randomization.

Intention-to-treat analysis assigns subjects to the groups to which they were randomized, regardless of whether they actually followed the assigned treatment, adhered to the protocol, or dropped out. This preserves the original randomization, so the comparison reflects the treatment strategy as it would be used in practice and avoids biases that come from excluding nonadherent participants or reclassifying them by the treatment they ended up receiving. Per-protocol analysis, for example, would analyze only those who followed the protocol, which can distort the treatment effect; as-treated analysis looks at the treatment actually received, which can introduce bias if reasons for switching are related to prognosis. Randomized-block refers to the way randomization was organized rather than how outcomes are analyzed, so it’s not about assigning to groups after randomization.