Lec 11. Bias and Misclassification Flashcards Preview

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Flashcards in Lec 11. Bias and Misclassification Deck (34)
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1
Q

Researches evalutate 3 aspects of their study (internal validity) before declaring a real true association, what are they?

A

Check for Counfounders or effect modifiers, check for bias and check for statistical significance.

2
Q

What is bias?

A

Systematic (NOT RANDOM) error in study design or conduct leading to erroneous results.

3
Q

What does bias do to the relationship between exposure and outcome?

A

Distorts it

4
Q

Can bias be fixed once it already occurred (after study ends)?

A

No

5
Q

How can you minimize bias and its impact?

A

Prospective (pre-study) consideration and adjustment

6
Q

What are three elements of bias?

A

Source/type, Magnitude/Strength and Direction

7
Q

What is Magnitude/Strength pertaining to one of the elements of bias?

A

Can account entirely for a weak association (RR/OR) but not likely for a very strong one

8
Q

What is Direction pertaining to one of the elements of bias?

A

Can over or under estimate true association. Towards or away from the ratio of 1.0

9
Q

What are the two main categories of Bias?

A

Selection-related and Measurement-related

10
Q

What is selection-related?

A

How we go and pick people, this will screw up soley by pts you pick.

11
Q

What is a way to avoid selection-related bias?

A

Dont do anything that is different between groups

12
Q

What is measurement related bias?

A

Anything we are measuring into observation, all data collection. Errors in here

13
Q

What is a way to avoid measurement-related bias?

A

Dont do anything that is different between groups

14
Q

What is selection bias?

A

The way study subjects are selected in different ways causing differences between groups

15
Q

What are examples of selection bias?

A

Healthy-worker bias, self-selection/participant(responder) bias

16
Q

What is Healthy-worker bias?

A

Only ppl included in study are those who are healthy enough to be there. The sick and dead are left out. w/ environmental studies

17
Q

What is self-selection/participant(responder) bias?

A

Those who wish to volunteer maybe different than those who didnt volunteer

18
Q

Pertaining to measurment bias via subject-related what are some examples?

A

Recall bias, Hawthorne effect, Contamination bias, compliance/adherence bias, Lost to follow up bias (Differential attrition)

19
Q

What is recall bias?

A

Pts recall things differently,memories etc

20
Q

What is Hawthorne effect?

A

Pts act differently because they know they are being watched

21
Q

What is contamination bias?

A

Control group receive treatment not part of study, altering results

22
Q

What is compliance/adherence bias?

A

Pts dont comply with medication/treatment

23
Q

What is lost follow up (differential attrition) bias?

A

Pts leave due to side effect etc

24
Q

Pertaining to measurement bias via observer related bias what are some examples?

A

Interviewer bias, diagnosis/surveillance bias, lead-time bias, publication bias

25
Q

What is interviewer bias?

A

Anything the interviewer does that is different from the 2 groups

26
Q

What is Diagnosis/surveillance bias?

A

Different interviewers have different skills/view points. Screen related.

27
Q

What is lead-time bias?

A

Pts screened and are becoming aware of disease longer than those unaware.

28
Q

What is publication bias?

A

Not everything gets published. Only want positive or desired outcome for researchers or authors.

29
Q

What is misclassification bias?

A

Error in classifying either disease or exposure status, or both. Source of measurement bias.

30
Q

What are two primary forms of missclassifcation?

A

Non differential and differential

31
Q

What is non differential and differential?

A

Non differential: mistakes happen equally in both groups (OR/RR) move to 1. Accept errors. Differential: Mistakes happen in one group unequally. RR/OR either direction

32
Q

What are two ways to control for bias?

A

Blinding/masking, and Randomly allocate observers/interviewers for data collection

33
Q

What is blinding/masking?

A

We use multiple sources to gather info

34
Q

what is Randomly allocate observers/interviewers for data collection?

A

Building many methods necessary to minimize loss to follow up.