Important equations Flashcards
death rate
death / census x number in question e.g per 100,000
rate
frequency of observed state or event / total number in whom this state or event MIGHT occur
prevalence rate
number of people with disease or condition at a specified time (x10n) / number of people in the population at risk at a specified time
incidence rate
number of people who develop a disease in a specified time period (x10n) / number of people in the population at risk of developing the disease at the specified period
prevalence
incidence rate x average duration of disease
case fatality
number of deaths from a disease in a specified period / number of diagnosed cases of the disease in the same period
crude mortality rate
number of deaths in a specified period (x10n) / average total population during the period
SMR
observed number of deaths / expected number of deaths x 100
point prevalence
number of ill ppl / population on that date
period prevalence
Number of cases that occurred in a given period ÷ Number of people in the population during this period
person years
number of subjects x age
odds ratio
odds of exposure in those with the disease / odds of exposure in those without the disease. absolute risk / probability of survival (A / B) / (C / D)
probability of survival
1 - absolute risk
relative risk
incidence exposed / incidence unexposed A / (A + C) / B (B + D)
AR
IR in exposed - IR in unexposed
