Undestanding Terms
Aggregation. The level at which data of the same type are gathered or grouped together. For instance, specific address data can be grouped together and displayed in blocks, census tracts, etc.
Analysis. The process of identifying a question or issue to be addressed, investigating multiple possible solutions, interpreting the results of that investigation, and possibly making a recommendation.
Average. The result obtained by dividing the sum total of a set or group of numbers by the total number in that group. Use caution when using this type of calculation, as high numbers in a set or very low numbers in the set skew the average number and distort the picture of what the indicator is supposed to express.
Baseline. The average rate or level of some variable at a point in time. It is generally understood that the baseline is the "before" measure that will be used for future comparison. Thus, the baseline is the measure prior to an intervention or strategy, and can be used as the starting point for tracking a trend.
Base map. A map containing geographic features used for location reference. Roads and properties, for example, are commonly found on base maps.
Benchmark. A point of reference or a standard against which measurements can be compared.
Census. The Decennial Census is the census (or complete enumeration) of population and housing, taken in each year ending in zero. Article 1, section 2 of the Constitution requires that a census be taken every 10 years for the purpose of apportioning the U.S. House of Representatives. The first census of population was taken in 1790. The Census Bureau first conducted the census of housing in 1940.
Census tract. A small, relatively permanent statistical subdivision of a county or statistically equivalent entity (Like Baltimore City) delineated for statistical data presentation purposes. Census tracts generally contain between 2,500 and 8,000 people, with an optimum size of 4,000 people. Census tracts vary in actual size because they are based on the number of people in the area, not the number of miles. Census tract boundaries are delineated with the intention of being stable over many decades, so they generally follow relatively permanent visible features. However, census tract boundaries always follow governmental unit boundaries: the boundary of a state or county (and Baltimore City) is always a census tract boundary. Census tracts do not cross jurisdictional boundaries.
Census block. The smallest geographic entity for which the Census Bureau tabulates census data.
Census block group. A cluster of census Blocks generally containing 300 to 3,000 people, with an optimum size of 1,500.
Community Statistical Areas (CSA). The data and indicators used on the BNIA website and for the Vital Signs are presented along Community Statistical Areas (CSA), which are clusters of Baltimore City's neighborhoods organized along U.S. Census Tract boundaries. These CSAs are used for statistical display of data only, and are not to be confused with neighborhoods as defined by neighborhood residents and others. This clustering was necessary because many neighborhood boundaries do not align with standard statistical boundaries such as U.S. Census tracts. The CSA map is becoming a standard way to display data about Baltimore City neighborhoods, and is used by the Alliance and several of the organizations affiliated with the Alliance. The CSAs were initially developed by the Baltimore City Planning Department and the Baltimore City Data Collaborative in 1998 by combining census tracts that have similar demographics, income, and education levels, as well as follow "logical" neighborhood and geographic areas. Map details are available by contacting the Alliance office.
Data. The purest definition of data is "information collected". Data are often thought of as statistical or quantitative, but they may take other forms-such as transcripts of interviews or videotapes of social interactions. Data are often coded-or quantified-to make them easier to analyze. Data then becomes statistical evidence from which conclusions can be inferred
Data Inventory. The list of data items that the Alliance currently has. The Inventory also lists the years when the data were collected, the lowest level of aggregation, the source, and the source's website information.
Data set. A collection of related data items.
Geographic Data. Information that pertains to a specific point or area on a surface of the globe; for example streets, census tracts, neighborhoods, zip codes, etc. Maps allow users to see a variety of information about geographic areas.
Geographic Information System. (GIS). An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display a number of data items on maps.
Index. A number derived from a series of observations or other data and used as an indicator or measure
Indicator. A measure that helps to quantify, express, or "indicate" the achievement and/or progress toward an outcome or goal. The indicator is the statistic or measure (or set of measures) that helps describe the social/physical condition. The indicator may be used to measure achievement or progress toward an outcome but in its purest definition it is the measure alone. It answers the question: "What will indicate to us we are reaching the goal?"
Median. The number that falls in the middle between the highest number and the lowest number in a series of numbers. The median is different than an average, which considers all the numbers in the calculation. With an average, high numbers in a set or very low numbers in the set skew the resulting number and distort the picture of what the indicator is supposed to express.
Metadata. Data about data; descriptive statistical information about the elements of a set of data
Numerator. The part of a fraction that is above the line and signifies the number of parts of the denominator taken. Example: the number of vacant and abandoned residential properties (numerator) is divided by all residential properties (the denominator) in the area to understand the magnitude of the vacant and abandoned problem in Baltimore City.
Outcome. The desired change (overall result) in behavior or condition you hope to achieve - Examples: well-being for children, adults, families or communities, and/or the environment (e.g. children born healthy, children succeeding in school, economically sufficient families, clean environment.).
Outcome Indicator. An indicator of the desired condition or result. Outcome Indicators (sometimes called outcome Measures) are used to understand the progress toward the overall Outcome.
Output. See Performance Indicator
Overlay. To cover the surface of something with something else. In mapping terms, to cover a map with a set of data that is formatted into a map layer. Data for mapping purposes is converted onto a "map layer." Map layers are placed over other map layers when mapping data.
Parcel level maps. Maps that display the outlines of street, property lines, blocks and more.
Percent. A given part of a whole, meaning that 100% of something is all of it. 50% of something is half of that whole.
Performance Indicator. (sometimes called a Process or Program Indicator. Most commonly known as an "Output".) An indicator used to gauge effectiveness of an agency or program service delivery. For example - an indicator of how well an agency or program is providing a service to customers (e.g. citizens - police response time, staff turnover rate, percentage of customers served in their own language, percentage of clients off alcohol and drugs)
Proxy. A temporary or substitute indicator. In some cases, data are not available to depict the indicator or concept desired. A proxy indicator is chosen as a way to explain the condition we are describing.
Qualitative data. Data that is non-numerical, or not easily reduced to numbers, collected for the purpose of discovering underlying meanings and patterns of relationships. For instance, what people think about their own neighborhoods, or how neighbors feel about their neighborhood, is qualitative data.
Quantitative data. Numerical information that can be summarized in statistics for analysis purposes.
Rate. A calculation of the amount or degree of something in relation to units of something else. For example, the number of juveniles ages 10-17 arrested per 1000 juveniles is the juvenile arrest rate.
Spatial data. Information about the location and shape of, and relationships among, geographic features, usually stored as coordinates and topology.
Static Map. A map that is non-interactive.
Statistics. Numerical summaries of data. Descriptive statistics are procedures for summarizing, organizing, graphing, and, in general, describing quantitative information. Inferential statistics are statistical techniques that allow you to draw conclusions from the data.
Trend. A direction demonstrated through observation of data over time. For example, the violent crime rate has decreased over the past few years. Let's hope this trend continues.
Trend analysis or time series analysis. Tracks a variable over time and uses statistical techniques to determine whether any changes in the variable are occurring by chance or because of an intervention. The time series analysis adjusts the trend line to account for seasonal changes and other influences.
