For this paper, you will need to find scholarly articles, statistics, and assessment validation. This page lists a few recommended places to search for these sources. See the Psychology guide for more.
Remember to apply the CRAAP test to evaluate your source: is it current? Is it relevant to your project? Who is the author, and why should we rely on them for this? Is it accurate and backed up with cited evidence? Finally, what is the purpose--is it sharing scientific research, or trying to persuade someone?
You will need to show that the assessment (test/measure/scale/whatever) is valid, so it actually measures what it's trying to measure. You can search for this in a psychology database by searching for the name of the assessment AND valid*
You can also check for this in the Mental Measurements Yearbook. This is a print book set in the Reference section of the Trustee Library (REF BF176 .B87). You can check which volume might have your assessment at this website: https://buros.org/tests-reviewed-mental-measurements-yearbook-series . Tip: press CRTL-F and search the name of your assessment to find it on the page.
Freebie for anyone using Social Readjustment Rating Scale:
The official name of the test is the Social Readjustment Rating Scale or the Holmes-Rahe Stress Inventory. Neither of these names appear in the MMY so you will have to use the databases to seek validation studies in the databases. When looking for validation it is easier to find information using Holmes Rahe than SRRS.