Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Epidemiology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

What are the three questions to find out confounders?

A

Q1: is the variable a risk factor/protective factor for the outcome?
Q2: is the variable associated with the exposure?
Q3: is the variable not an intermediate in the causal pathway?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is selection bias in a cohort study?

A

When there is a difference in the loss to follow up or enrollment procedures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the target population in a cohort?

A

The population you want the study to be generalizable to

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the source population in a cohort?

A

People who can join in the study

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the study population in a cohort?

A

People who start the study with you (reply to the invitation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the population for analysis in a cohort study?

A

People with all data available

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which populations differ from each other when external validity is not good?

A

The source population differs from the target population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which type of selection bias is likely with cross-sectional and case-control studies?

A

Selective enrollment issues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which type of selection bias is likely with prospective cohorts and RCTs?

A

Selective loss to follow up?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which populations differ from each other when selection bias occurs?

A

study population from the source population or population for analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the disadvantages of a cross-sectional study?

A

reverse causality, assessment of prevalence, selection bias (enrollment)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the disadvantages of a cohort study?

A

Expensive, time-consuming, confounding, external validity (effect modification), long enough follow up time?, selection bias (loss to follow up), information error

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the advantages of a cohort study?

A

Cause and effect is clear, rare exposures can be studied, possible to investigate exposure over time, possible to study many different outcomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the study outcome of a cross-sectional study?

A

Prevalence ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the outcome of prospective studies?

A

IRR/IPR = RR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the outcome of case-control studies?

A

OR (estimate of IRR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

With what study designs do you match cases with controls?

A

(nested) case control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the weaknesses of a case-control?

A

Selection bias (enrollment), information error (recall bias), confounding (reduced by restriction/matching/stratification), effect modification, reverse causation, hard to define exposure afterwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the advantages and disadvantages of looking at prevalence vs incidence in a case-control?

A

Prevalence: more cases but they could have changed their exposure
Incidence: no changed exposure but you need to interview people very soon after their diagnosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the advantages and disadvantages of looking at hospital-based vs population-based controls in a case-control?

A

Hospital based controls: potential information errors are the same as in the cases, but selection could be related to the exposure
Population based controls: they are more representative for the source population, but it is hard to reach the population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the advantages of a case-control?

A

You can study rare diseases and many risk factors at once

22
Q

What are the weaknesses of a RCT?

A

Ethical, short term, fixed exposure, intermediary endpoints, high risk populations, effect modification, selection bias

23
Q

Is the case cohort a prospective or retrospective design? And what type of bias is therefore limited?

A

Prospective, recall and selection bias

24
Q

What people are the comparison in a case cohort?

A

A random sample of the whole cohort: sub-cohort. They are all free of disease at baseline

25
Q

What are the advantages of a case-cohort?

A

Efficiency, reduces selection bias and recall bias, can be used for multiple diseases and sub-cohort can be used to calculate person-time risk

26
Q

What are the disadvantages of a case-cohort

A

Need large cohort, reduces power, loss to follow up, no matching, potential sample degradation

27
Q

Is the nested case control a prospective or retrospective design? And what type of bias is therefore limited?

A

Prospective, recall and selection bias

28
Q

Describe the selection of cases and controls in a nested case control study

A

Cases are all new cases of the disease and each control is sampled from the cohort with incidence density sampling

29
Q

What are advantages of the nested case-control?

A

Efficiency, reduction of selection and recall bias

30
Q

What are disadvantages of the nested case-control?

A

Reduced power, case-control pairs can only be used for 1 outcome, person time is not estimate

31
Q

When does selection bias occur?

A

When those selected to be in the study differ from those not selected

32
Q

Is selection bias a threat for internal or external validity?

A

Internal

33
Q

What are two types of selection bias?

A

Enrollment and follow up

34
Q

What are two types of information error?

A 
Measurement errors (continuous variables)
Classification errors (discrete variables)
35
Q

What will happen with a distribution when there are random errors?

A

The distribution will become wider -> more people in the tips.

36
Q

What is sensitivity and specificity regarding information error?

A

Sensitivity: percentage of the exposed that are correctly classified
specificity: percentage of the unexposed that are correctly classified

37
Q

How can you check for confounding when looking at graphs?

A

Draw an imaginary line through the data

38
Q

If the crude OR is 3, and the stratified ORs are 1,5 and 1,5 is it confounding or effect modification?

A

Confounding

39
Q

If the crude OR is 3, and the stratified ORs are 4 and 1,5 is it confounding or effect modification?

A

Effect modification

40
Q

How can you control confounding?

A

Through the design (restriction and matching)

Through data analysis (stratification, multivariable modelling)

41
Q

Will the power increase or decrease when the effect size will get larger?

A

Increase

42
Q

Will the power increase or decrease when the variance will get smaller?

A

increase

43
Q

Will the power increase or decrease when the sample size will get smaller?

A

Decrease

44
Q

Will the power increase or decrease when the alpha will get bigger?

A

Increase

45
Q

What is counterfactual thinking?

A

What if the situation would be exactly the same but with 1 thing different

46
Q

How can you imitate counterfactual thinking?

A

With well controlled RCTs

47
Q

What is additivity, synergism and antagonism in the causal model of rothman?

A

No interaction, and interaction

48
Q

If the background risk is low, are you more or less likely to pick up a high RR?

A

More likely

49
Q

What do you do when the heterogeneity is high with a meta-analysis?

A

Try to stratify or subgroup analysis

50
Q

What is a sensitivity analysis?

A

Exclude studies with a high risk for bias

51
Q

How can you check for publication bias?

A

With funnel plots, if it is symmetric, there is no publication bias.

52
Q

What is the difference between fixed and random effect models?

A

Fixed: you assume that there is 1 true association
Random: assume populations differ from each other

Epidemiology (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions