magnifying glass on a desk of scattered letters image.

Data Series

The collection of data characteristics of the target population repeated over time.


Reference information about a data series, responding unit, or single observation. Dimensions are characteristics used to group data into distinct groups such as race, gender, or fields of study.


A summary (mean, mode, total, index, etc.) of variable values for the responding units, such as the total number of doctorate recipients, median salary, and average annual R&D expenditures. In a dataset, the instance of a measure is often referred to as an observation.

Statistical Significance

Attained when statistical procedure applied to a set of observations yields a p value that exceeds the agreed level of probability which determines the null hypothesis will be rejected.

Statistical Survey

A data collection whose purposes include the description, estimation, or analysis of the characteristics of groups, organizations, segments, activities, or geographic areas. This type of survey may be a census or may collect information from a sample of the target population. Examples of population characteristics that may be explored in NCSES surveys are people, universities, or government entities.


The subject or area of analytical interest for users exploring data or conducting research. Example topics may include fields of study, research and development activity, or college or university enrollment.

Unweighted Count

The actual number of responding units found in a particular dataset, table, or measure before any necessary weighting has been applied to the table.


A characteristic of an object of study in a dataset that may take on more than one of a set of values to which a numerical or categorical measure can be assigned. Examples of common variables include occupation, sex, age, and industry.

Weighted Count

A weighted count represents the proportion of the target population that the responding unit in a survey represents. Users should use the weighted count when creating measures about the larger population from a sample survey.