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Definitions

The following technical terms are used in Public Health data publications.

Age-adjusted mortality rate - A mortality rate statistically modified to eliminate the effect of different age distributions in the different populations.

Age-specific mortality rate - A mortality rate limited to a particular age group. The numerator is the number of deaths in that age group; the denominator is the number of persons in that age group in the population.

Comparability ratio - Mortality data are coded using the International Classification of Diseases, Tenth Revision (ICD-10). Before 1999, deaths were coded using ICD-9. To ensure reliable trending of data over time, comparability ratios are applied to ICD-9 data so that they may be compared to the death data coded with ICD-10.

Confidence interval - A range of values for a variable of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable. The specified probability is called the confidence level, and the end points of the confidence interval are called the confidence limits. Confidence intervals can be used to approximate statistical significance.

Demographic information - The "person" characteristics — age, sex, race, and occupation — of descriptive epidemiology used to characterize the populations at risk.

Health indicator - A measure that reflects, or indicates, the state of health of persons in a defined population, e.g., the infant mortality rate.

Incidence rate - A measure of the frequency with which an event, such as a new case of illness, occurs in a population over a period of time. The denominator is the population at risk; the numerator is the number of new cases occurring during a given time period.

Increase/decrease - The terms "increase" and "decrease" indicate that a rate has had a statistically significant change over time.

Mortality rate - A measure of the frequency of occurrence of death in a defined population during a specified interval of time.

Prevalence - The number or proportion of cases or events or conditions in a given population.

Prevalence rate - The proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

Proportion - A type of ratio in which the numerator is included in the denominator. The ratio of a part to the whole, expressed as a "decimal fraction"(e.g., 0.2), as a fraction (1/5), or, loosely, as a percentage (20%).

Public health surveillance - The systematic collection, analysis, interpretation, and dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community.

Rate - An expression of the frequency with which an event occurs in a defined population.

Risk factor - An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or inherited characteristic that is associated with an increased occurrence of disease or other health-related event or condition.

Sample - A selected subset of a population. A sample may be random or non-random and it may be representative or non-representative.

Similar - When data are described as "similar" this indicates the difference is likely due to chance as opposed to a real difference between two populations, even if the data points are different. For example, if the rate for any given year or group of years is significantly higher or lower than the HP 2010 goal (using 95% confidence intervals) the rate is described as significantly higher or lower than the goal. If the goal falls within the confidence interval, the rate is described as similar to the goal.

Statistical significance - Data analysis includes a measure of whether an apparent difference between two figures (e.g., rates of disease for county and state) represents a real difference between the two figures, versus being due to chance. If statistical analysis determines that there is less than a 5% likelihood that the difference between two data points is due to chance, we say that the difference is "statistically significant", and we consider the two data points to be different.

Trend - A long-term movement or change in frequency, usually upwards or downwards.

Many of the above technical definitions were taken from the Centers for Disease Control and Prevention’s Reproductive Health: Glossary.

 

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