Introduction Overview rates measure event frequencies in a defined population during a specific time period rates are helpful in comparing event frequency in various places or times with varying population sizes Mortality Rates Crude mortality rate describes the total number of deaths per years per 1,000 people equation number of deaths during a certain time interval/mid-interval population size login to view 1 more bullet Cause-specific mortality rate describes the mortality rate caused by a certain disease or cause e.g., aggressive malignancy equation number of deaths by a certain disease during a certain time interval/mid-interval population Infectious Disease Rates Attack rate a type of incidence measure that is usually used in outbreak epidemiology e.g., gastrointestinal infection in patients caused by contaminated food equation number of patients with the disease during a certain time interval/total population at risk during that interval Case-fatality rate equation number of deaths by a certain disease during a certain time interval/total population affected by the disease during that interval Reproductive Rates Crude birth rate equation number of live births/total populations size Maternal mortality rate equation number of maternal deaths during a certain time interval/number of live births during that interval Neonatal mortality rate equation number of deaths of children < 28 days old during a certain time interval/number of live births during the same time interval Infant mortality rate equation number of deaths among children < 1 year of age during a certain interval/number of live births during that interval similarly, can calculate under 5 mortality rate as well Rate Standardization Rate standardization involves adjusting rates to allow for a comparison of frequency in populations with differing characteristics that may confound the results e.g., if disease X is more common in older people and population A has a higher proportion of older folks in their population, without adjustment to account for these age differences, it may appear that individuals in population A are at higher risk of a disease when in fact a population-level factor (age structure) is confounding the risk association Age is most commonly adjusted for Two main methods of standardization direct calculate expected rates of deaths (or disease cases) in studied population if it had a standarized structure with regards to the variable to be adjusted for login to view 2 more bullets first use a "standard" population structure login to view 2 more bullets multiply each strata of the population (e.g., age groups) by specific rates observed for those strata in each population under study to get the expected cases add up all strata of expected cases and divide the total expected cases by the standard population total to get standardized rates indirect calculate expected number of deaths (or disease cases) in studied populations using standard population rates login to view 2 more bullets first choose a "standard population" with variable-specific rates (e.g., rates of death in various age groups) multiply number of people in each variable group in the study population by the standardized rates to get the expected number of deaths add the expected number of deaths together and divide the total observed deaths in study population by the expected deaths login to view 1 more bullet