Definitions Flashcards
What is a Census?
Simultaneous recording of demographic data to all persons in a defined area
What is the Crude birth rate?
Number of live births per 1000 population
What is the General birth rate?
Number of live births per 1000 fertile women between age of 15-44
What is the Total period fertility rate?
Average number of children born to a hypothetical women in her lifetime
What is an Incidence rate?
The number of new cases of the disease per 1000 people per year (or 1000 person–years)
What is Prevalence?
The amount of people who currently have the disease in a set population (with no time frame)
What is Incidence rate ratio?
Incidence rates of two separate populations, with varying exposure, can be compared to see if exposure causes certain diseases
What is a confounder?
Something that is associated with both the outcome and the exposure of interest, but is not on the causal pathway
What is Standardised mortality rate?
The number of observed deaths / Number of expected deaths x 100
What is Variation?
A difference between the ‘observed’ and the ‘actual’ value
What is the lower confidence interval?
value ÷ error factor
What is the upper confidence interval?
value x error factor
What is the P value?
States how likely the results in the study would have occurred by chance if the null hypothesis was true.
What is Bias?
Deviation of the results from the truth via certain processes
What is Selection bias?
Error due to systematic differences in the ways in which the two groups were collected
What is Information bias?
Error due to systematic misclassification of subjects in the group
What are the 2 types of Selection bias?
Allocation bias
Healthy worker effect
What are the 2 types of Information bias?
Recall bias
Publication bias
What is a Cohort study?
Recruiting disease free individuals and classifying them according to their exposure status. Followed up for extended periods, disease progress is monitored, and incidence rates are calculated
What is Internal comparison?
Have sub-cohorts within your original group and then compare exposed and unexposed within the cohort. Uses IRR
What is external comparison?
Have your exposed population compared against a reference population instead. Uses SMR
What is the Healthy worker effect?
Employed individuals are more likely to be healthy than unemployed individuals as they work
What is a Case control study?
Recruit disease-free (controls) individuals and diseased individuals (cases) and then exposure status is determined
What is Double blinding?
Patient and doctor don’t which treatment they are on, removing any selection bias
What is the Bradford Hill criteria?
Strength of association Specificity of association Consistency of association Temporal sequence Dose response Reversibility Biological plausibility Coherence of theory Analogy
What is Clinical equipoise?
Reasonable uncertainty into which drug is better for the patient, so not subjecting patients to known less effective treatment
What is Ethical recruitment?
Recruitment for region where drug will take affect and no unethical exclusions from the trial
What is Valid consent?
Participants given sufficient knowledge, cooling off period, chance to ask questions, and ability to withdraw from trial at any point
What is Voluntariness?
No coercion or manipulation into entering the trial
What is a Systematic review?
A compilation of primary studies
What is a Meta analysis?
Provide quantitative synthesis of the primary studies used in the trial
What is the Fixed effects model?
Assumes the studies used are homogenous and any variation between data comes from within-study variation
What is the Random effects model?
Assumes the studies are heterogeneous and variation between data comes from within-study variation and between-study variation
What is Publication bias?
Studies are only likely to be published if results are statistically significant or have a large sample size. Funnel plots can determine Publication bias
How does a Forest plot display information?
Square size linked to weight in study
Diamond is overall measurement
Tips of diamond represent confidence intervals
What does it mean if the null value lies within the 95% CI?
The result may be due to chance, we cannot reject the null hypothesis.
What does it mean if the 95% CI excludes the null value?
The association is unlikely to be due just to chance.
What is reverse causality?
Possible that the cause-effect relationship exists, but in the opposite direction
What is the Henle Koch postulates?
Necessary - cause always precedes disease
Sufficient - cause alone leads to disease
Specific - cause absent in other diseae
Outline steps in RCT
Allocate
Follow up
Assess
Compare
What is the placebo effect?
Psychological benefit from being cared for, or differently, and being on a new treatment.
What are the types of outcome?
Patho physiological
Clinically defined
Patient focused
What are the features of an ideal outcome?
Appropriate/relevant Valid and attributable Sensitive and specific Reliable and robust Simple and sustainable Cheap and timely
What is an explanatory trial?
An as treated analysis. The non compliers are excluded
What is a pragmatic trial?
Intention to treat analysis. Better indication of drug in real life as non compliers are kept in
What makes a clinical trial ethical?
Clinical equipoise (not knowing which treatment is better)
Scientifically robust
Ethical recruitment
Valid consent
