This distinction can be a bit confusing. Briefly, a published test has a commercial publisher and is available for a fee and with controlled access--usually to a licensed psychologist. Use a resource like Tests in Print or Mental Measurements Yearbook to get the relevant information about the publisher, fees and terms. While certainly many of them are expensive, some are fairly inexpensive and can be used with the oversight of your professors.
Unpublished tests are in fact published, but usually in journals. These tests are generally available for use with permission. Many times you'll be able to find the authors' contact info within PsycINFO or the article in which you find it. Use tools like PsycINFO to find articles in which such tests appear, or you may also use books which collect and index citation information for these tests. Find examples of some of these indexes in the box to the right.
PsycTESTS®, produced by the American Psychological Association (APA), serves as a repository for a growing selection of psychological tests and measures, including thousands of actual test instruments and test items that are available for immediate download and use in research and teaching.
The interface looks like PsycINFO, but the contents are restricted to tests. Use words associated with what you want to measure. You may want to search PsycINFO first, to get a sense for the best terminology to use.
Note that in addition to finding it linked above on this guide, you may also find it in the Psychology & Counseling category of the Databases & Sources by Subject section of the library's website or BLink tab.
One of the best ways to find tests (AKA measures, scales, instruments, surveys, questionnaires, assessment, evaluation) is to search the journal literature in your discipline. For Psychology research, the best place to look, hands down, is PsycINFO.
OK. But how? It's easy, really. Once you formulate your search (see the "Search Tips" section of this guide on the "Find Articles" tab), add a variety of terms commonly used to describe assessment or evaluation, like this:
Among your results, you'll find various studies that use some kind of instrument. Sometimes these are reproduced within the article, and sometimes only mentioned. If you need to find a test that is mentioned in an article, check the reference list to see its source. You can also try searching the database using the name of the test. Not all of these will be available to students, but some will. Remember that professional ethics require that if the article does not explicitly grant permission to use a test reproduced in its entirety, you should attempt to contact the author for permission. Contact information is usually provided within the PsycINFO record. Or ask your friendly librarian for help!