Q. What types of sources am I allowed to use for research?
Research comes in many forms and can use many types of resources. You should always carefully review your assignment to determine the types of sources that are appropriate. Generally speaking, you should use scholarly resources. Scholarly resources are those that are written by a professional in that field and are written with the purpose of furthering research and/or informing you on a topic. Journal articles are the most common form of scholarly resource and the easiest to identify. However, books and websites can be scholarly as well.
For websites, you need to know who the author is and what their qualifications are before you will know it is scholarly. Is a journalist a professional who has in-depth experience and knowledge about criminal justice? Probably not. They are a professional at reporting news but not at about criminal justice, business, health, etc. When it comes to websites, .edu and .gov websites are generally more scholarly and trustworthy than the common .com websites.
Ultimately, the resource you use depends on your assignment and information need. If you need information on a recent event then you want a newspaper. If you want factual, background information, you want an encyclopedia or dictionary. If you want research that helps explain relationships between two or more variables or broadens knowledge of certain phenomena, you probably want journal articles. Books can provide many of these same bits of information but usually take a long time to publish and offer a broader context of information rather than presenting very specific research like a journal article would.