Numbers/statistical things Flashcards
Define epidemiology
study of frequency, distribution and determinants of disease and health
Define incidence
new cases over unit of time
Define prevalence
the number of a particular case at one point in time
What is absolute risk
your absolute risk of getting something.
so if 50 die of boredom from public health out of 250 population the absolute risk is 50/250 = 20%.
what is person time
used for calculating incidence
the idea being you made a bad study and not everyone was in it from the beginning or made it to the end. so you add up their disease free time. oh and if they die too.
So three people, 5 years. one person lasts 3 years then gets bored and leaves. another dies after 2 years and the other heroically makes it through the 5 years and graduates med school.
1/10 person-time units (3+2+5) = 10% incidence
=0.1 per person year = 10 per 100 person-years
attributable risk
how much disease is due to exposure
incidence of death in those exposed to X MINUS incidence of death in those NOT exposed to X
(X-noX)
relative risk - what are the digits
incidence of death in those exposed to X DIVIDED BY incidence of death in those NOT exposed to X
(X/noX)
lets say the attributable risk is low but relative risk is very high. Why might that be?
(As compared to something with a high attributable risk and low relative risk)
disease is rare :)
number needed to treat
1/absolute risk reduction
In a randomised controlled trial, the time at risk was determined from entry to
the study to various end points
whats this talking about
Person-years
In a case-control study of recent alcohol consumption and road traffic accidents, the measure of association was substantially greater than 1 and indicates that there is a positive association between exposure and outcome.
whats this talking about
Odds ratio
