Bias is defined as which of the following?

Bias is defined as which of the following?

• A. A systematic error or influence that causes an estimated treatment effect to deviate from the true effect
• B. Random variation in results
• C. A measure of study size
• D. A statistical test used to adjust for confounding

Answer: (A)

Bias refers to a systematic error or influence that causes an estimated treatment effect to deviate from the true effect. This means the distortion is consistent and directionally biased, not due to random fluctuation. It can arise from how participants are selected, how information is measured, or how confounding factors are controlled, and it threatens the study’s internal validity. In contrast, random variation reflects imprecision from sampling; a measure of study size describes how large the sample is; and a statistical method to adjust for confounding is a tool to reduce bias, not a definition of bias itself.

Bias refers to a systematic error or influence that causes an estimated treatment effect to deviate from the true effect. This means the distortion is consistent and directionally biased, not due to random fluctuation. It can arise from how participants are selected, how information is measured, or how confounding factors are controlled, and it threatens the study’s internal validity. In contrast, random variation reflects imprecision from sampling; a measure of study size describes how large the sample is; and a statistical method to adjust for confounding is a tool to reduce bias, not a definition of bias itself.