SUBJECT: MAINTAINING DATA SERIES OVER TIME

NCES STANDARD: 2-5

PURPOSE: To maintain and report NCES data series that are consistent over time.

KEY TERMS: bridge study, consistent data series, crosswalk study, and key variables.

STANDARD 2-5-1: NCES must maintain and report on a consistent set of data series that may be analyzed over time. Ongoing data collections must maintain and report on a consistent set of key variables, which are based on consistent data collection procedures.

GUIDELINE 2-5-1A: Identify the basic key variables to be assessed on a regular basis to address policy issues and other information needs.

GUIDELINE 2-5-1B: Provide estimates of both change and level for time series data in reports. For survey reports, consider publishing 3 or more years of the time series data along with the current year to highlight the time series.

GUIDELINE 2-5-1C: Provide a list of other publications containing the data for previous years in the appendix of a survey report.

STANDARD 2-5-2: Continuous improvement efforts sometimes result in a trade-off between the desire for consistency and a need to improve a data collection. If changes are needed in key variables or survey procedures for data series, a plan must be developed that provides the justification or rationale for the changes in terms of their usefulness for policy-makers, conducting analyses, and addressing information needs. The plan must also describe adjustment methods, such as crosswalks and bridge studies that will be used to preserve trend analyses.