07. Chance&Bias Flashcards
Systematic error
Error that is unintentionally “built into” a study; CONSISTENT DISTORTION in DIRECTION or magnitude of the results. Results in BIAS!!!
Random error
Outcome secondary to RANDOM CHANCE; reflects amount of variability; Unpredictablein direction or amount; REDUCED WITH LARGER SAMPLE SIZE
Confidence interval & Random Error
More random error widens the confidence interval; Use CI to express uncertaint in estimates d/t sampling error
Interpreting bias
Toward the null (underestimated); away from the null (overestimated)
Types of bias
Selection bias; Information bias; Confounding bias
Selection bias
Systemic error; non-random selection of sample from population
Information bias
Systematic error; Inaccuracy in measurement or classification of study variables
Confounding bias
Systematic error of interpretation from making UNFAIR COMPARISON; FAILUR to take into account IMPORTANT DIFFERENCES between groups
Types of selection bias
Sampling bias; Ascertainment bias (surveillance; Referral/admission; Diagnostic); Participation bias (self-selection/volunteerism; non-response/refusal; Healthy worker effect/survival)
Non-differential bias
Everyone measure equally, but incorrectly; Bias towards the null
Differential bias
One group is measured DIFFERENTLY; bias is unpredictable
Limitations
Natural conditions that restrict boundaries of study & may affect outcomes
Delimitations
restrictions imposed in order to narrow the study boundaries
Precision
absence of random error
Reliability
the consistency of a study (tight grouping on bullseye); repeatable
