HaDPop Flashcards
Define a census
Simultaneous recording of demographic data of all persons in a defined area
What are some uses of a census?
Allocation of resources, population projections and seeing trends
What is crude birth rate?
Live births per 1000 population
What is gross fertility rate?
Live births per 1000 women aged 15-44
What is total period fertility rate?
The average number of children born to a hypothetical woman in her lifetime (birth rate of each age bracket)
What is crude death rate?
Number of deaths per 1000 population
What is prevalence?
Amount of people who have the disease in a set population
What is standardised mortality rate?
Mortality rate that takes into account confounding factors, mainly age and sex.
How is standardised mortality rate worked out?
(observed deaths/expected deaths) x 100
What is incidence rate?
Number of new cases of the disease per 1000 people per year
How is incidence rate worked out?
New cases exposed/(population x years)
What is an incidence rate ratio?
A comparison of the incidence rates of two populations with varying exposures
How is incidence rate ratio worked out?
( New cases exposed/(population x years) ) / ( New cases unexposed/(population x years) )
What is a confounding factor?
Factor associated with both outcome and exposure, but not causal
What are confidence intervals?
A range of values in which we can be 95% confident that the true value lies within
What is the relationship between the null hypothesis and confidence intervals?
If the 95% confidence interval contains zero (more precisely, the parameter value specified in the null hypothesis), then the effect will not be significant at the 0.05 level.
What is selection bias?
Bias due to systematic difference in the way two groups are collected
What is information bias?
Bias due to systematic misclassification of subjects in a group
What is the healthy worker effect?
People at work are likely to be more healthy, or be exposed to certain things. They can’t be compared to reference population unless it is another working group.
What does a cohort study involve?
Recruiting disease free individuals, classifying by exposure status, following up and calculating incidence rates
What types of exposures is a cohort study good for studying?
Rare
What is the difference between prospective and retrospective studies?
Prospective- disease free individuals, followed up after exposure
Retrospective- disease free individuals recruited and exposure status calculated from historical data
What is the difference between internal and external comparisons, in cohort studies?
Internal- comparison between sub cohorts within larger cohort. Comparison of exposed and unexposed within cohort so IRR used
External- comparison with reference population. SMR used
What does a case-control study involve?
Disease free controls and diseased cases recruited and odds ratio worked out to determine exposure status
Can you work out odds ratio?
-
Can you work out error factor?
-
What does an odds ratio of 1 show?
Null hypothesis
What is the benefit of having more controls?
Error factor size reduced
How are confounders removed in a case-control study?
Matching
What is the effect of randomisation?
Confounders removed
Why is intention to treat analysis better?
More valid, as reflects how drug would be used
What are the Bradford-Hill criteria and what do they determine?
Biological plausibility, strength of association, specificity of association, consistency of association, dose response, temporal sequence, coherence of theory. They determine causality
How can compliance be measured?
Blood and urine testing
What are some ethical considerations in undertaking a randomised control trial?
Is it good for population? Ethical recruitment, consent and clinical equipose
What is a systematic review and meta-analysis?
Analysis of primary studies and quantitative synthesis of primary studies
What is a funnel plot useful in showing?
Publication bias. A well balanced systematic review will have funnel shape
What is publication bias?
Only using published studies (which are more likely to show statistical significance)
What is the difference between the fixed effects model and the random effects model?
Fixed effects- assumes studies are homogenous and variation comes from within-study variation
Random effects- assumes studies are heterogenous and variation comes from within-study variation and between-study variation
What are the advantages of systematic reviews?
Explicit methods, meta analysis gives overall figure, clinically useful and fits into evidence based practice
