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performance_bias
Performance bias occurs when the groups in a study receive systematically different treatment, care, or attention beyond the intervention being studied. This can happen when participants or care providers know the group assignment and consciously or unconsciously alter their behavior. The observed outcome differences then reflect not just the studied intervention but also these unintended co-interventions.
In an unblinded trial of a new surgical technique, surgeons using the new technique also provide more attentive post-operative care, while patients in the standard surgery group receive routine follow-up. The new technique appears superior, but the extra attention confounds the comparison.
A clinical trial testing a new antidepressant is unblinded, and psychiatrists who know their patients are on the new drug schedule more frequent check-in calls and offer additional counseling sessions. Improved outcomes in the treatment group are partly attributable to the extra support rather than the drug itself.
In an educational study comparing a new reading curriculum to the standard one, teachers assigned to the new curriculum receive special training workshops and ongoing coaching, while teachers using the standard curriculum receive none. Students in the new curriculum perform better, but it is unclear whether the curriculum or the extra teacher support drove the improvement.
Binary (yes/no) questions an LLM must answer to identify this aspect:
Did the comparison groups receive different levels of attention, care, or co-interventions beyond the studied treatment?
Type: binaryWere participants or care providers aware of group assignments?
Type: binaryCould knowledge of treatment assignment have changed participant behavior or clinician decisions?
Type: binaryWere co-interventions and ancillary care standardized across all groups?
Type: binaryPerformance bias occurs when the groups in a study receive systematically different treatment, care, or attention beyond the intervention being studied. This can happen when participants or care providers know the group assignment and consciously or unconsciously alter their behavior. The observed outcome differences then reflect not just the studied intervention but also these unintended co-interventions.
People modify their behavior when they know they are being observed or treated differently. Patients who know they received the 'better' treatment may be more optimistic and compliant. Clinicians may provide better care to patients they believe are on a promising treatment.
Blind participants and care providers to treatment assignment where possible. Standardize all aspects of care except the studied intervention. Monitor and report co-interventions in all groups. Use sham procedures or active placebos when blinding is otherwise impossible.
Open-label drug trials consistently show larger treatment effects than double-blinded trials for the same drug. The difference is attributable to performance bias: when doctors and patients know the treatment, behavior changes in ways that amplify the apparent benefit.
Systematic differences in how outcomes are identified between comparison groups.
Researcher expectations systematically influence how observations are recorded.
Treatment groups differ in baseline risk, confounding the treatment effect.
Failing to account for a third variable that influences both the independent and dependent variables, creating a spurious apparent relationship. The 'lurking variable' problem that undermines causal claims from observational data.
Measurement error that differs between comparison groups, biasing results in either direction.
Use these tools to detect, analyze, or train this aspect.