 NCES 2006-005October 2005

## Guide To Tabular Presentation

This section is intended to assist the reader in following the basic structure of the Digest tables and to provide a legend for some of the common symbols and indexes used throughout the book. Unless otherwise noted, all data are for the 50 states and the District of Columbia.

### Table Components

Title Describes the table content concisely.

Unit indicator Informs the reader of the measurement unit in the table"In thousands," "In millions of dollars," etc. Noted below the title unless several units are used, in which case the unit indicators are generally given in the spanner or individual column heads.

Spanner Describes a group of two or more columns.

Stub Describes a row or a group of rows. Each stub row is followed by a number of dots (leaders).

Field The area of the table which contains the data elements. Special notes Symbols used to indicate why data do not appear in designated cell.

  Not available. † Not applicable. # Rounds to zero. ! Interpret data with caution. ‡ Reporting standards not met.

Footnote: Describes a unique circumstance relating to a specific item within the table.

Note: Furnishes general information that relates to the entire table.

Source: The document or reference from which the data are drawn. This note may also include the organizational unit responsible for preparing the data.

### Descriptive Terms

Measures of central tendency:  A number that is used to represent the "typical value" of a group of numbers.  It is regarded as a measure of "location" or "central tendency" of a group of numbers.

Arithmetic mean (average) is the most commonly used average.  It is derived by summing the individual item values of a particular group and dividing that sum by the number of items.  This value is often referred to simply as the "mean" or "average."

Median is the measure of central tendency that occupies the middle position in a rank order of values.  It generally has the same number of items above it as below it.  If there is an even number of items in the group, the median is the average of the middle two items.

Average per capita, or per person, figure represents an average computed for every person in a specified group, or population.  It is derived by dividing the total for an item (such as income or expenditures) by the number of persons in the specified population.

Index number   A value that provides a means of measuring, summarizing, and communicating the nature of changes that occur from time to time or from place to place.  An index is used to express changes in prices over periods of time, but may also be used to express differences between related subjects at a single point in time.

Arithmetic mean (average) is the most commonly used average. It is derived by summing the individual item values of a particular group and dividing that sum by the number of items. This value is often referred to simply as the "mean" or "average."

Median is the measure of central tendency that occupies the middle position in a rank order of values. It generally has the same number of items above it as below it. If there is an even number of items in the group, the median is the average of the middle two items.

Average per capita, or per person, figure represents an average computed for every person in a specified group, or population. It is derived by dividing the total for an item (such as income or expenditures) by the number of persons in the specified population.

Index number A value that provides a means of measuring, summarizing, and communicating the nature of changes that occur from time to time or from place to place. An index is used to express changes in prices over periods of time, but may also be used to express differences between related subjects at a single point in time.

The Digest most often uses the Consumer Price Index to compare purchasing power over time.

To compute a price index, a base year or period is selected. The base-year price is then designated as the base or reference price to which the prices for other years or periods are related. When 100 is subtracted from the index number, the result equals the percent change in price from the base year.

Current and constant dollars are used in a number of tables to express finance data. Unless otherwise noted, all figures are in current dollars, not adjusted for inflation. Constant dollars provide a measure of the impact of inflation on the current dollars.

Current dollar figures reflect actual prices or costs prevailing during the specified year(s).

Constant dollar figures attempt to remove the effects of price changes (inflation) from statistical series reported in dollar terms.

The constant dollar value for an item is derived by dividing the base-year price index (for example, the Consumer Price Index for 1999) by the price index for the year of data to be adjusted and multiplying by the price of item to be adjusted. The result is an adjusted dollar value as it would presumably exist if prices were the same as the base yearin other words, as if the dollar had constant purchasing power. Any changes in the constant dollar amounts would reflect only changes in the real values.

NOTE: Tables may not include data for all years implied in table titles. When this is the case, the title will include the term "Selected years."