Definitions Flashcards
Active Surveillance
The surveillance of an outcome by searching for cases in the community
Allocation
The distribution of study subjects to intervention and control arms in an intervention study
Allocation Concealment
In a randomised-controlled trial
Allocation not revealed to the person enrolling subjects to reduce selection bias
Alternative Hypothesis (H-Theta)
The opposite of the null hypothesis, but may indicate the direction of an association
Analytical Study
Designed to test a hypothesis. Generally examines whether a particular exposure is a risk factor for a particular outcome
Ascertainment Bias
A type of information bias, where detection of an outcome may vary between exposure groups. Found in intervention studies without blinding
Asymptomatic
Non-symptomatic outcome
Attributable Fraction
A measure that calculates the attributable risk as a proportion of the incidence of outcome in those exposed
Attributable Risk
A measure that calculates the additional incidence of outcome in those exposed after subtracting the incidence that would have occurred in the absence of exposure i.e. no. of cases that could be prevented if the exposure was completely eliminated
Assumes the link is causal
Can be calculated from risks or incidence rates
Bias
A systematic difference from the truth
Blinding
Where information about exposure or outcome is concealed from the participants and/or observers to reduce information bias
Case
An individual that meets the case definition for having the outcome of interest
Case-Control Study
An observational study in which 2 groups are defined on the basis of their outcome status (cases have exposure, controls don’t).
Levels of exposure to a risk factor is then measured between the groups and compared.
Odds ratio is the only measure or relative risk that can be obtained from case-control studies. No measure of the frequency of the outcome.
Case Definition
Criteria for identifying an individual as having the health outcome of interest
Case-Fatality Rate
The proportion of cases with an outcome, which are fatal within a specified time period
Causal Pathway
The sequence of events leading from an exposure to an outcome
Causality
The relationship between an exposure and a health outcome, where the outcome is considered to be a consequence of the exposure
Chance
The possibility of observing a value or event within reason or predictability i.e. not representative
Cluster-Randomised Trial
Participants are randomised into groups rather than as individuals
Cohort Study
An observational study in which two groups are defined on the basis of their exposure to a potential risk factor over time to measure the incidence of the outcome which is then compared to give an estimate of relative risk
Compliance Risk
The proportion of individuals who co-operate fully
Component Cause
A factor that contributes to producing an outcome
Confidence Interval
The range of values estimated from a sample within which the ‘true’ value is likely to be found
Confounder
A variable that is associated with both the exposure and outcome but it not in the causal pathway that is being investigated and may provide an alternative explanation for any association observed