Exam 2: Bias & Misclassification

Question 0

What is the definition of Bias?

Answer 0

Systematic (non-random) error in study design or conduct leading to erroneous results.

Question 1

How can researchers be assured they found a TRUE relationship between “exposure” and “outcome”?

Answer 1

They need to evaluate 3 aspects of their study (internal Validity)

1) Check for Bias
2) check for confounding or effect modification (interaction)
3) Check for statistical significance

Question 2

What does bias do?

Answer 2

distorts the relationship (association) between exposure and outcome.
*design flaw.

Question 3

After calculating various measures of association (RR/OR/HR), how can researchers assess internal validity (study design/methodology) for areas of possible error?

Answer 3

By check for bias, bias is one those possible sources of error

Question 4

What can be done to “fix” a bias one it has already occurred?

Answer 4

Nothing can be done to fix it.

Question 5

How can bias and it’s impact be minimized?

Answer 5

Prospective (pre-study) consideration and adjustment.

Question 6

What 3 components do investigators evaluate when assessing for bias and its impact?

Answer 6

1) Source/Type
2) Magnitude/Strength
3) Direction

Question 7

T/F bias can account entirely for a weak association (small RR/OR/HR) but is not likely to account entirely for a very strong association (large RR/OR/HR)

Answer 7

TRUE

Question 8

How can bias affect the direction of a measure of the true association?

Answer 8

They can over or under-estimate the true measure.

Question 9

In relation to the null hypothesis does a bias have any effect?

Answer 9

yes, a bias can have an enhancing or minimizing effect on the true measure of association (towards or away from the null hypothesis)

Question 10

Define information/observation/measurement -related biases:

Answer 10

any aspect in the way the researcher collects information, or measures/observes subjects (and their variable) which creates a systematic difference between groups in the quality/accuracy of their information.
*errors in measurement or classification (misclassification)

Question 11

What are selection-related biases?

Answer 11

Any aspect in the way the researcher selects subjects (cases or controls, exposed or unexposed, study sample) which creates a systematic difference in the composition between groups.

Question 12

What is a commonly seen selection-related bias?

Answer 12

When comparing groups not coming from same population/group or not being representative of the full population.

Question 13

What is a selection bias?

Answer 13

Selecting study subjects that are not representative of your primary population of interest or that generates differences in groups being compared (very commonly encountered)

Question 14

What are 3 key examples of selection bias?

Answer 14

1) Healthy-worker bias
2) self-selection/participant (responder) bias
3) control selection bias

Question 15

Define self-selection/participation (responder) bias.

Answer 15

those that wish to participate (volunteer) may be different in some way to those that don’t volunteer or self-select (refusal/non-response) to participate

Question 16

When can a control selection bias be easily seen?

Answer 16

In a Case-Control study.

Question 17

What issue do you run into with information/observation/measurement bias?

Answer 17

Subject-related variations

Observer-related Variations.

Question 18

What is a recall (reporting) Bias?

Answer 18

A subject-related bias.
A differential level of accuracy/detail in provided information between study groups. exposed or diseased may have greater sensitivity for recalling their history, or the severity may amplify their response.

Question 19

What is the Hawthorne effect?

Answer 19

A subject-related variation in which individuals can report their “effects” of exposure, disease symptoms or Tx differently b/c they are part of a study.

Question 20

What is a contamination Bias?

Answer 20

a Subject-related variation in which members of the control group accidentally, or outside of the study protocol, receive the Tx (or similarly) or are exposed to the intervention being studied.

Question 21

What is compliance Bias?

Answer 21

a subject-related variation in which the groups being interventionally studied have different compliances. ( just don’t take rx b/c of side effect)

Question 22

What is a Lost to Follow-up bias?

Answer 22

A subject-related variation in which the groups being studied have different withdrawal or lost to follow-up rates OR there are other differences between those that stay in the study and those that withdraw or are lost to follow-up
** differential vs. non-differential.

Question 23

Can a lost to follow-up occur in a cohort study?

Answer 23

Yes, in a prospective cohort. While waiting for the disease to occur they can be lost to follow-up

Question 24

What is interviewer (proficiency) bias?

Answer 24

an observer-related variation.

-A systematic difference in soliciting, recording, or interpreting on the part of the researcher (or their assistants)

Question 25

What type of bias would have an issue with the interviewers knowledge influence the response from the study subjects, either conscious or unconscious?

Answer 25

Interviewer (proficiency) bias.

Question 26

How can you assure that you will get the same info with multiple people involved when interviewing pts?

Answer 26

Take the interviewer out of the equation. I.e Have a recording, or by not providing additional info if pts have questions.

Question 27

What is a diagnosis/surveillance (expectation) bias?

Answer 27

Different eval/classification/Dx/observation between study groups.

Observers may have preconceived expectation of what they should find in exam/eval/follow-up

Question 28

What is it called when the researcher is trying to make the study have the results they believe should be there?

Answer 28

Hawthorne-like effect

Question 29

What is kappa statistic?

Answer 29

Agreement between evaluators

Question 30

T/F blinding didn’t work if they pt doesn’t know what drug they were on.

Answer 30

False. Blinding did work!

Question 31

How can you control for biases?

Answer 31

Select most precise, accurate, & medically-appropriate measures of assessment and eval/observation

Question 32

What are ways you can have the highest sensitivity/specificity and valid screening tools?

Answer 32

Use published/past-utilized techniques, if possible.

Calibrate & test equipment, techniques and processes.

Question 33

List 4 options for controlling biases:

Answer 33

1) blinding/masking
2) use multiple sources to gather all info
3) randomly allocate observer/interviewers for data collection (train them)
4) build in as many methods necessary to minimize loss to follow-up

Question 34

Define misclassification:

Answer 34

error in classifying either disease or exposure status, or both

Question 35

Define non-differential misclassification

Answer 35

misclassification of exposure or disease which is unrelated to the other.
Effect= for dichotomous (2) variable, bias can move the measure of association (RR/OR/HR) towards the null hypothesis.

Question 36

define differential misclassification:

Answer 36

error in one group differently than other.
misclassification of exposure or disease is related to the other
effect= bias can move the measure of association in either direct in relation to the null hypothesis. can inflate or attenuate your effect estimates of association.