Psychological measures are typically purchased from commercial publishers. The following sites offer some that are at no financial cost.
Finding Published and Unpublished Testing Instruments The APA provides guidance in using available resources to find psychological tests. Answers to frequently asked questions are provided in the FAQ
APA Science Directorate Testing and Assessment Page
Databases
Educational Resources Information Clearinghouse (ERIC) - is a complete bibliography of educational materials available since 1966. Indexes published and unpublished sources on thousands of educational topics, with information from from RIE (Resources in Education) and CIJE (Current Index to Journals in Education), and including materials focused on every aspect of educational testing.
The General Social Survey (GSS) The GSS contains a standard 'core' of demographic, behavioral, and attitudinal questions, plus topics of special interest. Many of the core questions have remained unchanged since 1972 to facilitate time-trend studies as well as replication of earlier findings. The GSS takes the pulse of America, and is a unique and valuable resource. It has tracked the opinions of Americans over the last four decades.
Health Services and Sciences Research Resources (HRSS) contains Information about research datasets and instruments/indices employed in Health Services Research, Behavioral and Social Sciences, and Public Health with links to PubMed. Rather than being an archive of datasets and instruments themselves, the HSRR is a searchable online database of records, i.e., categorical descriptions of datasets and instruments.
Medline (PubMed) Search the Clinical Queries to quickly find systematicreviews, etiology, diagnosis, therapy and prognosis.
Mental Measurements Yearbook produced by the Buros Institute, contains full-text information about and reviews of all English-language standardized tests covering educational skills, personality, vocational aptitude, psychology, and related areas as included in the printed Mental Measurements Yearbooks.
The National Quality Measures Clearinghouse™ (NQMC), sponsored by the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services, is a searchable public repository and Web site for information on specific evidence-based health care quality measures and measure sets. NQMC is sponsored by AHRQ to promote widespread access to quality measures by the health care community and other interested individuals.
Psych Info is an index of publications that the APA examines regularly to identify psychologically relevant material, including journal articles, dissertations, reports, English-language book chapters and books, and other scholarly documents. The TM field ["tests and measures" field] contains the names of published tests and measures mentioned in the source document. Psych Info also contains evaluative journal articles.
Books
Tests in Print
Educational and Psychological Tests in the Academic Library
Standards for Educational and Psychological Tests
Adapting Educational and Psychological Tests for Cross-Cultural Assessment
