Epidemiologic Measures: 4 types
Count Number of cases of disease or other health phenomenon being studied
Ratio “the value obtained by dividing one quantity by another” X/Y=ration (Friis & Sellers, 2021). COVID Deaths/Deaths from all causes=ratio 0.024=51684/2152651
Incidence Rate: The rate of development of a disease in a group over a certian time period; this period of time is included in the denominator including 1) a numerator 2) a denominator and 3) time (Friis & Sellers, 2021).
Proportion* “a type of ratio in which the numerator is part of the denominator" (Friis & Sellers, 2021). Proportion=A/(A+B)X100
Prevalence: the number of existing cases of a disease or health condition in a population at some designated time (Friis & Sellers, 2021). My Example: 51684 COVID death cases in 2023
Point Prevalence: Number of cases of illness in a group or population at a point in time divided by the total number of persons in that group or population.
Point prevalence=number of persons ill/total number in the group (at a point in time) (Friis & Sellers, 2021). My Example: COVID Deaths in 2023/Death from all causes 51684/2152651=0.02400946553
Period Prevalence: Number of cases of illness during a time period divided by the average size of the population. Period Prevalance= number of persons ill/average population (during a timer period) (Friis & Sellers, 2021). My Example: COVID death cases in 2023 compared to USA population 51684/334,914,895=0.0001543198*
Sex Ratio has 3 variations:
References
Friis, R. H., & Sellers, T. A. (2021). Epidemiology For Public Health Practice (6th ed.). Jones and Bartlett Learning.
Deaths by Select Demographic and Geographic Characteristics. (2020, May 13). Www.cdc.gov; Centers for Disease Control and Prevention. https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm
Demographic Sex Ratio: "The number of males per 100 females" (number of males/number of females)x100
Sex Ratio at Birth: (number of male births/number of female births)X1000
Simple Sex Ratio: number of male cases/number female cases=male to female cases
My Example-Cases of COVID 2020 in males/females=sex ration (Deaths by Select Demographic and Geographic Characteristics, 2020)
629728/517,046=1.218
My Example (629728/517,046)x100=121.8
This calculation reveals there are more males than females affected as the result is greater than 100 (Deaths by Select Demographic and Geographic Characteristics, 2020)
My Example-Males born at a rural hospital in 2023 vs females
(1826/1623)x1000=2.964
My Example- Proportion of cases of COVID vs all causes 2020-2023 all ages (Deaths by Select Demographic and Geographic Characteristics, 2020)
Proportion=1146774/(1146774+12303399)X100
Proportion=1146774/13450173X100
Proportion=A/(A+B)X100
COVID (A)-1146774
All causes (B)-12303399
Proportion=8.5%
My Example: total number of deaths of all causes in 2023 2152651
Adjusted: Rates of morbidity or mortality in a population in which statistical procedures have been applied to permit fair comparisons across populations by removing the effect of differences in the composition of various populations; an example is age adjustment (Friis & Sellers, 2021).
Crude: A summary rate based on the actual number of events in a population over a given time period. An example is the crude death rate, which approximates the proportion of the population that dies during a time period of interest (Friis & Sellers, 2021).
Specific: Statistic that refers to a particular subgroup of the population defined in terms of race, age, or sex; also may refer to the entire population but is specific for some single cause of death or illness, as in a cause-specific rate (Friis & Sellers, 2021).
My Example: Rate=death in a year from COVID/reference populationx100,000
Rate=12303399/336997624x100,000
Rate= 3650.89 per 100,000 deaths
Incidence Rate=Number of new cases over a time period/Total population at risk during the same time periodX100000
My Example: COVID Cases in 2020 compared to population of USA in 2020
(385666/329,500,000)x100000=117.046 COVID deaths per 100,000 persons
Attack rate: An alternative form of the incidence rate that is used when the nature of a disease or condition is such that a population is observed for a short time period. The attack rate is calculated by the formula ill/(ill + well) × 100 (during a time period). The attack rate is not a true rate because the time dimension is often uncertain (Friis & Sellers, 2021).