HadPop Flashcards
Define sensitivity
How good a test is at giving a positive result when the disease is actually present, so number of true positives divided by the number of true positives plus the number of false negatives.
Formula for SMR
SMR= (observed/expected)*100
Why use an SMR?
To adjust for confounding factors e.g. age.
Why do we calculate an error factor?
To see how much chance/random variation has affected our results.
How do you calculate an OR for a case-control study?
a x b/c x d where a= those with disease who were exposed, b= those without disease who were exposed, c=those with disease who were unexposed, and d=those without disease who were unexposed.
When does an OR approximate to relative risk?
When the disease studied is rare.
How can you reduce the influence of chance on the results of a case-control study, and so reduce the error factor?
Recruit more controls. No. controls usually 5X no. of cases.
What is the importance of randomisation in RCTs?
To remove the effect of known and unknown confounders and to minimise allocation bias.
Define incidence
the number of new cases of a particular disease in a defined population, over a given time period. Given per number of person-years.
Define prevalence
the number cases of a disease within a defined population, at a given point in time. Not given per unit time, so not a rate. Proportion.
Give advantanges and disadvantages of a case-control study.
Ad: - cheap
- quick
- good for rare diseases
Disad: -can’t prove temporal sequence
- subject to recall bias
- not good for rare exposures
What quantitative analysis is used in a systematic review?
Meta-analysis
What are the Bradford-Hill Criteria
Set of criteria to help determine is something if there is a causal relationship. Strength of association Consistency of association Temporal sequence Coherence of theory Reversibility Dose-response Biological mechanism Analogy
