07. Chance&Bias Flashcards Preview

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Flashcards in 07. Chance&Bias Deck (17):
1

Systematic error

Error that is unintentionally "built into" a study; CONSISTENT DISTORTION in DIRECTION or magnitude of the results. Results in BIAS!!!

2

Random error

Outcome secondary to RANDOM CHANCE; reflects amount of variability; Unpredictablein direction or amount; REDUCED WITH LARGER SAMPLE SIZE

3

Confidence interval & Random Error

More random error widens the confidence interval; Use CI to express uncertaint in estimates d/t sampling error

4

Interpreting bias

Toward the null (underestimated); away from the null (overestimated)

5

Types of bias

Selection bias; Information bias; Confounding bias

6

Selection bias

Systemic error; non-random selection of sample from population

7

Information bias

Systematic error; Inaccuracy in measurement or classification of study variables

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Confounding bias

Systematic error of interpretation from making UNFAIR COMPARISON; FAILUR to take into account IMPORTANT DIFFERENCES between groups

9

Types of selection bias

Sampling bias; Ascertainment bias (surveillance; Referral/admission; Diagnostic); Participation bias (self-selection/volunteerism; non-response/refusal; Healthy worker effect/survival)

10

Non-differential bias

Everyone measure equally, but incorrectly; Bias towards the null

11

Differential bias

One group is measured DIFFERENTLY; bias is unpredictable

12

Limitations

Natural conditions that restrict boundaries of study & may affect outcomes

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Delimitations

restrictions imposed in order to narrow the study boundaries

14

Precision

absence of random error

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Reliability

the consistency of a study (tight grouping on bullseye); repeatable

16

Validity

the accuracy of a study (how many times bullseye is hit); absence of bias or error

17

Systematic error: accuracy::

random error: precision