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CAPS II FInal > CAPS written exam > Flashcards

CAPS written exam Flashcards

1
Q

What is stratifying?

A

Stratifying means conducting separate analyses for each group

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2
Q

When is stratifying not useful?

A

When there are multiple confounders

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3
Q

What is the effect of stratifying on power?

A

It reduces power by reducing sample size

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4
Q

Randomization, matching and multivariate statistical adjustments are _

A

Alternatives to stratifying

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5
Q

What is an adjusted estimate?

A

The result of multivariable regression

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6
Q

What type of multivariate regression would you use for categorical (non-continuous) outcomes?

A

Multivariable logistic regression

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7
Q

What type of multivariate regression would you use for continuous outcomes?

A

Multiple linear regression

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8
Q

What type of multivariate regression would you use for time to event outcomes?

A

Multivariable Cox regression

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9
Q

In a y=mx+b model, the correlation coefficient (r) estimates _

A

how well outcome variable y can be predicted given variable x

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10
Q

Time to event data is best plotted using _

A

Kaplan Meier Survival curves

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11
Q

For a given survival curve, how do you calculate median survival time?

A

Find 50% on Y, extrapolate to X

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12
Q

What is censoring in survival data?

A

When the participant doesn’t participate for the duration of the experiment. (Reach outcome, lost to followup)

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13
Q

What is the log rank test?

A

A test to determine whether median survival is equivalent between groups (survival curve)

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14
Q

What is cox regression?

A

multivariable analysis of time-to-event data and is commonly seen in clinical trials and cohort studies.

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15
Q

A regression analysis that allows for statistical adjustment of hazard ration is _

A

Cox regression

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16
Q

The output of cox regression is _

A

Hazard ratio

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17
Q

What is sensitivity?

A

Measures how well a test identifies the presence of disease when it is present

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18
Q

Sensitivity can be calculated as _

A

Sensitivity=TP/(TP+FN)

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19
Q

To rule out a diagnosis you’d want a test with high _

A

Sensitivity

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20
Q

What is specificity?

A

Measures how well a test identifies the absence of disease when it is absent

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21
Q

Specificity can be calculated as _

A

Specificity=TN/(TN+FP)

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22
Q

To rule in a diagnosis you’d want high _

A

Specificity

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23
Q

Screening tests have high _ while confirmatory tests have more _

A

Sensitivity

Specificity

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24
Q

Positive predictive value is calculated as _

A

PPV=TP/(TP+FP)

True positives out of all positives

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25
Q

Negative predictive value is calculated as _

A

NPV=TN/(TN+FN)

True negative out of all negatives

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26
Q

How is PPV influenced by prevalence?

A

In general, the positive predictive value of a test is greater when the disease is more prevalent in the population.

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27
Q

How is NPV influenced by prevalence?

A

When prevalence increases, NPV decreases.

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28
Q

What is likelihood ratio?

A

LR relates pre-test and post-test probabilities.

29
Q

LR+ is _

A

likelihood ratio for a positive test result

30
Q

LR- is _

A

likelihood ratio for a negative test result

31
Q

A high LR

A

increases the post-test probability relative to the pre-test probability

32
Q

A low LR

A

decreases the post-test probability relative to the pre-test probability (means the disease is less likely).

33
Q

How do you use a nomogram?

A

Connect the pretest probability and the LR (or post-test probability)

34
Q

Convenient appraisal _

A

Taking everything at face value
Reading only the abstract and relying on its conclusions
Reading the entire paper and relying on its conclusions

35
Q

Cynical appraisal _

A

Outright rejection of the paper due to one or two questions or concerns about the study, regardless of their importance
Ultimately, taking little or no value from a study

36
Q

Critical appraisal _

A

Systematically considering positive and negative aspects of a study’s approach

37
Q

Validity is a measure of accuracy. It may be reduced by _

A

Systematic error

38
Q

Three steps to assessing internal validity are _

A

Bias
Confound
Chance

39
Q

Bias is a systematic error. Selection bias affect _, while information bias affects _

A

Who ends up in the study

What end up in the study

40
Q

Over estimation or underestimation of effect can result from _ (2)

A

Bias

Confounding

41
Q

Suppose that 30 subjects in the placebo group and no subjects in the treatment group drop out due to illness. Because these dropouts are not counted in the calculations at the end of the study, this is a type of _

A

Selection bias

42
Q

Pts over-reporting certain types of behaviors / or under-reporting is a form of _

A

Information bias

43
Q

Ways to evaluate the effects of chance on data include _

A

Evaluation of p-value and confidence interval

44
Q

External validity is also known as _. It should be conducted after _

A

generalizability.

Internal validity assessment

45
Q

What are phase I, 2 and 3 trials?

A

first-in-man
small number of participants from the presumed target population
large groups of patients assigned to the new intervention or a control

46
Q

In clinical trials, information bias can be reduced by _ (2)

A

Placebo

Blinding

47
Q

What are single, double and triple blind studies?

A

Patients
Patients + clinicians
Patients, clinicians, data analysts

48
Q

Confounding can be reduced in clinical trials by _

A

Randomization

49
Q

In a clinical trial when participants in one group are more likely to drop out during the study period—say, due to the side effects of an intervention under study, this can violate _

A

Randomization

50
Q

What is intention to treat analysis?

A

participants in RCTs should be analyzed the same way that they were randomized at the beginning of the study

51
Q

NNT (number needed to treat) can be calculated by _

A

1/ARR (Absolute risk reduction)

52
Q

Absolute risk reduction is _

A

[Incidence in exposed group - incidence in non-exposed group]

53
Q

An NTT of 3.3 means _

A

four patients would need to be treated with the drug in order to prevent one case of dementia, on average

54
Q

In cohort studies,

A

Participants in a cohort study are selected and sorted based on the presence or absence of an exposure of interest. They are then followed for the development of an outcome of interest

55
Q

Confounding is more a problem is {RCT/cohort study]

A

Cohort study

56
Q

In a case control study _

A

participants are selected based on the outcome—that is, whether they are a case or a control—and are evaluated with respect to a prior exposure.

57
Q

Case control are [retrospective/prospective/both]

A

Retrospective. Out come already occured

58
Q

The best type of study for a rare disease (hard to find participants) is _

A

Case control

59
Q

The statistical outcome for a case control study is _

A

Odds ratio. Cannot calculate incidence rates since events have already occured

60
Q

A major difference between RR and OR is _ (relative to incidence rate)

A

RR takes incidence rates into account

61
Q

Recall bias is an especially difficult problem is what type of study design?

A

Case control

62
Q

Case control is outcome, look back
Cohort study is exposure, look forward (or back)
Cross sectional looks at exposure and outcome at same time

A

Nothing to see

63
Q

The major statistical outcome for cross sectional study is _

A

Odds ratio

64
Q

You can use cross sectional studies to assign causality. True or false _

A

False

65
Q

Two types of descriptive study designs are _

A

Case study

Case series

66
Q

When multiple causes contribute to an event, this is referred to as _

A

Multifactorial cause

67
Q

Competing causes _

A

Result in the same outcome via different mechanisms

68
Q

Effect modification is where _

A

effect of an exposure differs with the presence of another variable. The effect modifier interacts with the exposure to change the effect of the exposure on the outcome.

CAPS II FInal (2 decks)

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