Which type of bias occurs when the method of data collection leads to systematic differences between groups?

• A. Confounding
• B. Selection bias
• C. Information bias
• D. Recall bias

Answer: (C)

Information bias occurs when the way data is collected or measured introduces errors that are systematic rather than random, and these errors differ between groups. If the method of data collection, instruments, questionnaires, or interviews impact one group differently, the recorded data (exposures, outcomes, or other variables) will be biased, distorting the study results. Remember, recall bias is a specific form of information bias where memory differs between groups, but the general idea here is the measurement process itself causing systematic differences. Selection bias and confounding involve who is included or how variables relate, not the measurement method.