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Understanding Communities Count Data and Terms

Confidence Interval (also known as error bar) is the range of values that includes the true value 95% of the time. If the confidence intervals of two groups do not overlap, the difference between groups is considered statistically significant (meaning that chance or random variation is unlikely to explain the difference).   For some indicators, results are reported with a 90% confidence interval, showing the range that includes the true value 90% of the time.

Crude, Age-Specific, and Age-Adjusted Rates

  • Rates are usually expressed as the number of events per 100,000 population per year. When this applies to the total population (all ages), the rate is called the crude rate.
  • When the rate applies to a specific age group (e.g., age 15-24), it is called the age-specific rate.
  • The crude and age-specific rates present the actual magnitude of an event within a population or age group.
  • When comparing rates between populations, it is useful to calculate a rate that is not affected by differences in the age composition of the populations. This is the age-adjusted rate. For example, if a neighborhood with a high proportion of older people also has a higher-than-average death rate, it will be difficult to determine if that neighborhood’s death rate is higher than average for residents of all ages or if it simply reflects the higher death rate that naturally occurs among older people. The age-adjusted rate mathematically removes the effect of the population’s age distribution on the indicator.

Geographies: Whenever possible, indicators are reported for King County as a whole and for 4 regions within the county.  If enough data are available for a valid analysis, they may also be reported by smaller geographic areas (cities, neighborhoods within large cities, and groups of smaller cities and unincorporated areas).  Education data are reported by school district.  For more detail, plus maps, see About King County Geographies.

Health Reporting Areas (HRAs): In 2011, new King County Health Reporting Areas (HRAs) were created to coincide with city boundaries in King County.  HRAs are based on aggregations of U.S. Census Bureau-defined blocks.  Where possible, HRAs correspond to neighborhoods within large cities, and delineate unincorporated areas of King County. The new HRAs were designed to help cities and planners as they consider issues related to local health status or healthy policy.  HRAs are used whenever we have sufficient sample size to present the data. 


Definition: “Fundamentally, poverty is a denial of choices and opportunities, a violation of human dignity.  It means lack of basic capacity to participate effectively in society. It means not having enough to feed and clothe a family, not having a school or clinic to go to, not having the land on which to grow one’s food or a job to earn one’s living, not having access to credit. It means insecurity, powerlessness and exclusion of individuals, households and communities. It means susceptibility to violence, and it often implies living in marginal or fragile environments, without access to clean water or sanitation.”    United Nations Statement, June 1998, signed by the heads of all UN agencies.  

Federal Poverty Guidelines, issued by the Department of Health and Human Services, are a simplified version of the federal poverty thresholds.  The guidelines are used to determine financial eligibility for various federal, state, and local assistance programs. For a family of 4, the federal poverty guideline was $22,050 in 2010; in 2013 it was $23,550.

The Federal Poverty Threshold was adopted in 1964 as an “absolute measure” by which progress in the War on Poverty could be assessed. It is updated annually by the Census Bureau, and is used to calculate official population statistics on the number of Americans in poverty. Its usefulness has diminished over the past half century, as it almost certainly underestimates poverty in the United States. Specific shortcomings include:

  • Lack of adjustment for regional costs
  • Calculation based totally on the cost of food, ignoring significant contributions from housing, transportation, utilities, health care, and child care
  • Reliance on pre-tax earnings, excluding the effects of tax adjustments, food stamps, housing benefits, and other transfers.

Neighborhood poverty levels are based on the proportion of households in a Census tract in which annual household income (as reported in the U.S. Census Bureau’s American Community Survey) falls below the federal poverty threshold. 

  • High poverty: 20% or more households in the neighborhood below poverty threshold.
  • Medium poverty: 5% to 19% of households below poverty threshold.
  • Low poverty: fewer than 5% of households below poverty threshold.

Quotes:  Communities Count interviewed 32 King County parents or guardians raising at least one child younger than 6 years of age.  We reached out to communities of color, recent immigrants, and residents with limited English proficiency to achieve a broad range of racial, cultural, and socioeconomic diversity. We interviewed both families with very low household income and those who earned up to median income (about $68,000 for a family of four in 2010). Family structures included single-parent households, couples living in consensual unions, married couples, and extended families. We also interviewed social service providers from agencies such as Crisis Clinic, Hopelink, Multi-Service Center, and Child Care Resources, as well as staff from community colleges that offer worker retraining or similar programs to help King County residents find jobs. We use fictional names to ensure confidentiality.

Race/Ethnicity and Discrimination: Race and ethnicity are markers for complex social, economic, and political factors that can influence community and individual health in important ways. Many communities of color have experienced social and economic discrimination and other forms of racism that can negatively affect the health and well-being of these communities. We continue to analyze and present data by race/ethnicity because we believe it is important to be aware of racial and ethnic group disparities in health, income, housing, food hardship, and other indicators.  We hope this awareness will support the development of policies and priorities that promote equity and social justice in all our communities. 

When using survey data, the number of respondents in some racial and ethnic groups may be too small for reliable data analysis. When this happens, some groups may be combined to form broader and less meaningful categories, such as “white” and “people of color.” This clearly blurs the original group definitions and limits the interpretation of the analysis.  However, our commitment to reporting whatever statistical disparities exist across racial and ethnic groups led us to accept this compromise. 

Race/Ethnicity Terms: Federal standards mandate that race and ethnicity (Hispanic origin) are distinct concepts requiring 2 separate questions when collecting data from an individual. "Hispanic origin" is meant to capture the heritage, nationality group, lineage, or country of birth of an individual (or his/her parents) before arriving in the United States. Persons of Hispanic ethnicity can be of any race. Communities Count's terms for racial/ethnic groups are derived from those used by the U.S Census Bureau in 2010.

  • Communities Count terms:  Hispanic, Non-Hispanic, White Non-Hispanic, Black, American Indian/Alaska Native (AIAN), Asian, Native Hawaiian/Pacific Islander (NHPI), White, and Multiple Race (Multiple). Persons of Hispanic ethnicity can be of any race and are included in other racial categories. Racial/ethnic groups are sometimes combined when sample sizes are too small for valid statistical comparisons of more discrete groups. 
  • 2010 Census terms: Hispanic or Latino, Not Hispanic or Latino, White alone (Not Hispanic or Latino),  Black or African American, American Indian or Alaska Native, Asian, Native Hawaiian or Other Pacific Islander, White, Some Other Race, and Two or More Races.

Rolling averages:  When the frequency of an event varies widely from year to year, rates are sometimes aggregated into averages – often in 3-year intervals – to smooth out the peaks and valleys of the yearly data. For example, for events occurring from 2001 to 2010, rates may be graphed as three-year rolling averages: 2001-2003, 2002-2004…2008-2010. Adjacent data points will contain overlapping years of data. Statistical tests comparing data points with overlapping times are not appropriate.

Statistical Significance: Differences between groups are examined for each indicator.  Unless otherwise noted, all differences mentioned in the text are statistically significant (unlikely to have occurred by chance).

The potential to detect differences and relationships (termed the statistical power of the analysis) is dependent in part on the number of events and size of the population, or, for surveys, the number of respondents, or sample size. Differences that do not appear to be significant might reach significance with a large enough population or sample size.

Trend graphs for sub-populations are often shown as “rolling averages” (see definition above) that smooth the plotted lines, making it easier to observe changes – or the absence of changes – over time. For relatively small populations, slight changes in the number of events can cause the rate to fluctuate substantially, creating jagged lines of statistical “noise.”