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M1 S3 > Biostat Q2 > Flashcards

Biostat Q2 Flashcards

1
Q

Adjusted analysis

A

An analysis in which statistical account is made for potential confounding factors, so that an estimate of the independent effect of a risk factor can be made.

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2
Q

Cohort

A

A group of subjects followed over time

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3
Q

Competing risk

A

Events that prevent the observation of a possible endpoint

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4
Q

Confounding

A

An indirect association of an exposure with disease. Confounding is due to the asociation

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5
Q

Effect

A

The magnitude of a difference or relationship

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6
Q

Event

A

A clinical outcome of importance.

Examples include onset of a disease (such as cancer or heart disease), onset of a particular symptom (such as bleeding or depression), disease recurrence, or death.

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7
Q

Incidence

A

The risk or rate or occurrence of new cases of a disease

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8
Q

Matched analysis

A

Choosing exposed and unexposed subjects to have the same or similar values of some trait or exposure. Matching is typically done to control confounding.

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9
Q

Prevalence

A

The proportion of individuals with a particular disease or trait in a given population.

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10
Q

Rate

A

A measure of event frequency; the speed with which events happen, relative to the size of the population experience observed.

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11
Q

Rate ratio

A

A relative risk measure in which the numerator is the rate at which an event occurs in an exposed group, and the denominator is the rate in an unexposed group. See rate and relative risk.

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12
Q

relative risk

A

Strictly speaking a ratio of risks. The term is also used to refer to any relative measure of association: a ratio in which the numerator describes the occurrence of events (risk, rate, odds or hazard) in an exposed group, and the denominator describes the occurrence of events in an unexposed group.

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13
Q

Restricted analysis

A

Analysis confined to one group of subjects, to minimize confounding.

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14
Q

Risk

A

The probability that an event will occur in a defined period of time.

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15
Q

Risk difference

A

The difference between the risks of an exposed group and unexposed group during a defined period of time (the risk of disease attributable to exposure).

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16
Q

Risk factor

A

An exposure associated with the occurrence of a disease or outcome.

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17
Q

Risk ratio

A

A relative risk measure in which the numerator is the probability of an event occurring in an exposed group, and the denominator is the probability in an unexposed group. See risk and relative risk.

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18
Q

Stratum

A

A grouping of subjects, typically formed for the purposes of adjustment (e.g. age groups).S

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19
Q

Study type: DESCRIPTIVE

Once the research design has been determined, recall the points that may affect internal validity of that design, and assess the extent to which there may be problems. Decide if these are minor or critical issues for the study at hand

A

Points to consider:

–> No comparison: describe only what is possible, not what is better or worse.

–> Concern is the precision ( or lack of it) and bias in measurements

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20
Q

Study type: CASE-CONTROL

Once the research design has been determined, recall the points that may affect internal validity of that design, and assess the extent to which there may be problems. Decide if these are minor or critical issues for the study at hand

A

Points to consider:

–> Selection bias (do cases and controls correspond?).

–> Information bias (did the presence/absence of the disease affect the data obtained?).

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21
Q

Study type: COHORT

Once the research design has been determined, recall the points that may affect internal validity of that design, and assess the extent to which there may be problems. Decide if these are minor or critical issues for the study at hand

A

Points to consider:

–> Follow-up (were exposed and unexposed groups followed and endpoints determined with equal intensity, and without bias?).

aks 
follow-up study

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22
Q

Study type: CLINICAL TRIAL

Once the research design has been determined, recall the points that may affect internal validity of that design, and assess the extent to which there may be problems. Decide if these are minor or critical issues for the study at hand

A

Points to consider:

–> What kind of controls (randomized is best)?

–> Were all groups followed-up in the same (unbiased) way?

–>Was the randomization concealed from investigators and subjects? (Blinding helps assure this.)

23
Q

Study Type: ANY STUDY

Once the research design has been determined, recall the points that may affect internal validity of that design, and assess the extent to which there may be problems. Decide if these are minor or critical issues for the study at hand

A

Points to consider:

–> Adequate sample size to detect a meaningful effect?

–> Is confounding present?

–> Did people with the exposure of interest have the same chance to be detected to have the outcome as people without?

24
Q

Any valid study

A

Points to consider:

Generalizability aka external validity

25
Q

as-treated analysis

A

AKA efficacy analysis

A statistical analysis of data from a randomized clinical trial in which the outcome is evaluated according to the treatment actually received. This analysis procedure loses some of the advantages of randomization. (Contrast with intention-to-treat analysis)

26
Q

bias

A

A feature of a study tending to distort its findings away from the true result for the population being studied.

27
Q

blinding

A

–> The process of keeping clinical trial subjects and/or study personnel unaware of the treatment assignments.

–> Also used to describe the process of keeping study participants or personnel unaware of the hypotheses under study.

28
Q

case-control study

A

A research design in which subjects with a disease or outcome (cases) are compared to subjects without the disease/outcome (controls). (Improperly called a retrospective study.)

29
Q

case report

A

AKA case series

An informal study in which the experience of a group of patients is described, without a comparison group.

30
Q

clinic-based

A

A study in which all subjects are derived from patients seen at a medical facility. A hospital-based study is an example. (Typically used with regard to a case- control study.)

31
Q

clinical trial

A

A formal intervention study, in which the investigators determine the treatments or exposures of the subjects (usually by randomization).

32
Q

cohort study

A

A research design in which a defined group of subjects is followed over time for the occurrence of events. (Contrast with cross-sectional study. See also retrospective cohort study)

33
Q

cross-sectional study

A

A research design in which subjects are evaluated at only one timepoint. (Contrast with cohort study.)

34
Q

double-blind

A

A situation in which both subjects and investigators are unaware of the subjects’ treatments or exposures.

35
Q

ecological study

A

An investigation in which the unit of analysis is a group. Examples include correlation of trends over time in disease rates with trends in cigarette sales, or association of disease rates in different countries with cigarette sales.

36
Q

effectiveness

A

The impact of an intervention in usual clinical practice.

37
Q

efficacy

A

The impact of an intervention under ideal conditions.

38
Q

efficacy analysis

A

A statistical analysis of data from a randomized clinical trial in which the outcome is evaluated according to the treatment actually received. This analysis procedure loses some of the advantages of randomization. (Contrast with intention-to-treat analysis).

Analysis of only that group that complied with the treatment regimen

39
Q



external validity

A

The ability of a study to apply to populations other than the one actually studied. Also called generalizability.

40
Q

historical controls

A

A control group comprised of subjects whose past experience is contrasted with those of currently observed subjects. Historical controls are generally considered inferior to concurrent controls.

41
Q

information bias

A

A distortion caused by information provided by one group of subjects being systematically different than that provided by another group. This potential problem is usually associated with case-control studies, in which case patients may provide systematically different information than controls.

aka response bias

42
Q

intention-to-treat analysis

A

A statistical analysis of data from a randomized clinical trial in which outcome is evaluated according to the randomized treatment group, regardless of what treatment was actually received. This analysis procedure makes full use of the advantages of randomization. (Contrast with efficacy analysis).

Analysis of all patients who participated in the study regardless of whether or not they adhered to the treatment plan.

43
Q

internal validity

A

The ability of a study to reach a correct conclusion about the population actually studied.

44
Q

intervention study

A


A study in which the investigators determine the exposures or treatments for subjects. (Contrast with observational study.)

aka clinical trial

45
Q

observational study

A

A study in which the investigators do not determine the exposures or treatments subjects experience. (Contrast with intervention study.)

46
Q

odds ratio

A

A type of relative risk; the only type of relative risk possible in case-control studies. Calculated with a cross-product ratio from a 2 × 2 table.

47
Q

placebo

A



A sham drug used in blinded studies to keep subjects and/or investigators unaware of subjects’ treatment assignments.

48
Q

prospective study

A

An investigation in which the events studied occur during the time the research is conducted. (Contrast with retrospective study.)

49
Q

randomization

A

A way of assigning treatments so that each subject has the same probability of receiving a particular treatment. Randomization makes treatment “independent” of the subjects’ characteristics, and thus effectively “prevents” confounding.

50
Q

retrospective study

A


An investigation in which all of the events studied have already occurred at the time the research begins; existing records provide the data. (Contrast with prospective study.)

51
Q

retrospective cohort study

A

A study in which the exposure and outcome have already occurred: exposed and unexposed subjects are “followed” through time afterwards e.g. through review of medical records

52
Q



selection bias

A



A bias that arises because of the selection of subjects in a study.

53
Q

single blind

A

A situation in a clinical trial in which either the patient or the investigator group is unaware of treatment assignment, but not both. The term is best used to describe the situation in which the investigators evaluating endpoints are unaware of treatment assignment.

M1 S3 (6 decks)

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