Statistics

Statistics

The art and science of collecting, analyzing, presenting, and interpreting data.

Data

The facts and figures collected, analyzed, and summarized for presentation and interpretation.

Data set

All the data collected in a particular study.

Elements

The entities on which data are collected.

Variable

A characteristic of interest for the elements.

Observation

The set of measurements obtained for a particular element.

Nominal scale

The scale of measurement for a variable when the data are labels or names used to identify an attribute of an element. Nominal data may be nonnumerical or numerical.

Ordinal scale

The scale of measurement for a variable if the data exhibit the properties of nominal data and the order or rank of the data is meaningful. Ordinal data may be nonnumerical or numerical.

Interval scale

The scale of measurement for a variable if the data demonstrate the properties of ordinal data and the interval between values is expressed in terms of a fixed unit of measure. Interval data are always numerical.

Ratio scale

The scale of measurement for a variable if the data demonstrate all the properties of interval data and the ratio of two values is meaningful. Ratio data are always numerical.

Categorical data

Labels or names used to identify an attribute of each element. Categorical data use either the nominal or ordinal scale of measurement and may be nonnumerical or numerical.

Quantitative data

Numerical values that indicate how much or how many of something.

Quantitative data

are obtained using either the interval or ratio scale of measurement.

Categorical variable

A variable with categorical data.

Quantitative variable

A variable with quantitative data.

Cross-sectional data

Data collected at the same or approximately the same point in time.

Time series data

Data collected over several time periods.

Descriptive statistics

Tabular, graphical, and numerical summaries of data.

Population

The set of all elements of interest in a particular study.

Sample

A subset of the population.

Census

A survey to collect data on the entire population.

Sample survey

A survey to collect data on a sample.

Statistical inference

The process of using data obtained from a sample to make estimates or test hypotheses about the characteristics of a population.

Data mining

The process of using procedures from statistics and computer science to ex- tract useful information from extremely large databases.