Bias And Study Errors Flashcards

1
Q

Bias And Study Errors - recruiting participants

A

Selection bias

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2
Q

Bias And Study Errors - performing study

A
  1. Recall bias
  2. Measurement bias
  3. Procedure bias
  4. Observer-expectancy bias
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3
Q

Bias And Study Errors - Interpreting results

A
  1. Confounding bias

2. Lead time bias

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4
Q

Selection bias (type and definition)

A

Type: Recruiting participant bias

Error in assigning subjects to study group resulting in an unrepresentative sample. Most commonly a sampling bias

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5
Q

Selection bias examples

A
  1. Berkson bias (from hospitals)
  2. Healthy worker effects
  3. Non-response bias
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6
Q

Strategy to reduce selection bias

A
  1. Randomization

2. Ensure the choice of the right comparison/reference group

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7
Q

Berkson bias

A

Type of selection bias

Study population selected from hospital is less healthy than general population

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8
Q

Healthy worker effect

A

Type of Selection bias

Study population is healthier than general population

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9
Q

Non-response bias

A

Type of Selection bias

Participating subjects differ from nonrespondents in meaningful ways

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10
Q

Recall bias (type and definition)

A

Type: performing study

Awareness of disorder alters recall by subjects. Common in retrospective studies

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11
Q

Recall bias example

A

Patients with disease recall exposure after learning of similar cases

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12
Q

Recall bias strategy to reduce

A

Decrease time from exposure to follow up

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13
Q

Measurement bias (type and definition)

A

Type: performing bias

Information is gathered in a way at distorts it

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14
Q

Measurement bias example

A

Miscalibrated scale consistently overstates weights of subjects

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15
Q

Measurement bias strategy to reduce

A

Use objective, standardized and previously tested method of data collection that are planned ahead of time

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16
Q

Procedures bias (type and definition)

A

Performing study

Subjects in different group are not treated in the same way

17
Q

Procedure bias example

A

Patients in treatment group spend more time in highly specialized hospitals units

18
Q

Procedure bias strategy to reduce

A

Blinding and use of placebo reduce influence of participant and researchers on procedures and interpretation of outcomes as neither are aware of group allocation

19
Q

Observer-expectancy bias (type and definition)

A

Type: Performing study
Researchers belief in the efficacy of the treatment changes the outcome of that treatment (aka Pygmalion effect, self-fulfilling prophesy)

20
Q

Observer-expectancy bias example

A

If observer expects treatment groups to show signs of recovery, then he is more likely to document positive outcomes

21
Q

Observer-expectancy bias strategy of reduction

A

Blinding and use of placebo reduce influence of participant and researchers on procedures and interpretation of outcomes as neither are aware of group allocation

22
Q

Bias And Study Errors types

A
  1. Recruiting participants
  2. Performing study
  3. Interpreting results
23
Q

Interpreting results bias types

A
  1. Comfounding bias

2. Lead times bias

24
Q

Comfounding bias (types and definition)

A

Type: Interpreting bias
When factor is related to both exposure and outcomes, but not to the causal pathway –> factor distorts or confuses effects on outcome

25
Confounding bias example
Pulmonary disease is more common in coal workers than the general population. However, people who work in coal mines also smoke more frequently than the general population
26
Confounding bias strategy of reduction
1. Multiple/repeated studies 2. Crossover studies (subjects act as their own controls --> persons in group 1 receive the drug and group 2 placebo. Later they swich) 3. Matching (patient with similar characteristics in both treatment and control groups) 4. Restriction 5. Randomization
27
Lead-times bias type and definition
Type: interpreting results | Early detection is confused with increased survival
28
Lead time bias example
Early detection makes it seems as though survival has increased, but the natural history of the disease has not changed
29
Lead time bias strategy of reduction
Measure "back end" survival (adjust survival to the severity of disease at the time of diagnosis)
30
Recall bias is common in
Retrospective bias
31
Observer expectancy bias is also called
1. Pygmalion effect | 2. Self-fulfilling prophecy
32
Pygmalion effect is aka
1. Observer expectancy | 2. Self-fulfilling prophecy
33
Crossover studies
subjects in group 1 receive the drug and group 2 placebo. Later they switch --> subjects act as their own control
34
types of bias - groups
1. recruiting participants 2. performing study 3. interpreting results