I am writing a research paper (graduate level) on eating disorders. Many books have been written on this topic, ranging from pop culture type to scholarly works.
How do I know if a book is sufficiently reliable to use as a source in my paper? Am I looking for an author with a Masters degree? With clinical experience? With personal experience? Certain publishers? Or does anything go?
No field that I am aware of has a list of "officially approved sources". So there is nothing which formally forbids you from using a specific source.
However, your work will be judged based on not just its own qualities, but also the sources you use, and how you use them. Quoting a source just because it has a good, concise definition of a term is no big deal. But that same source might not be a good source for facts and numbers. Your average "pop culture" book will not document how those numbers were obtained.
Now for your specific case, I understand that the topic is eating orders, and not the public perception of eating orders or a similar meta-topic. In that case, you will likely be using academic definitions of your terms. So even if the pop literature would offer some concise, readable definitions of particular terms, they would likely not be the definitions used in the other sources that you will be quoting. So be consistent, and use the definitions from the academic sources.
"This shouldn't cause a problem: You needn't rely on a single source" Unfortunately, the reliability of a statement does not increase with the number of its repetitions. In mathematics life is easy: you just verify the proof yourself. In medicine you usually do not have an option to repeat the study and decide whether it is crap or not this way. All you can do is to find the original article (not a reference to a reference to a reference to...) and see if it is written in a clear and convincing way (so the design of the study makes sense and is well-explained, the statistical evaluation is correct, the conclusions do actually follow from the observations presented, etc.) If it is the case, you can use it as a "reliable source", if not, the doubts remain. Unfortunately, the common medical writing is often not up to these standards even when the research itself is good (my ex-wife is a doctor so I've seen plenty of articles and heard her comments about them as well). Then you are forced to take into account secondary indicators like how reputable the researchers or their institutions are. In general, it is better to err on the side of declaring something that makes sense crap than on the side on declaring some crap making sense, so just be as skeptical as you can and look for all kinds of possible flaws.
As a first approximation:
Meta-analyses and reviews are probably more reliable than single studies. Prefer them. If there are several, check that they agree. A review might be a (text)book, but articles are usually more common. Meta-analyses are probably articles.
(Text)books aimed at researchers and graduate students are the next step.
Particular experimental articles contain the state of the art, but you will need to check if they are reliable with more care than the other sources
To check the reliability of an article, check the methodology, check Pubpeer and consult senior researchers to figure out if there are problems with the articles or if the researchers have a good or a bad reputation, and check if there are several studies claiming similar results.
You might also want to check if the publisher is a known predatory publisher or a reputable scientific publisher, though this is by no means a reliable indicator. Wikipedia pages of publishers are a good place. I might also check the level of the journal in the Finnish Julkaisufoorumi database https://www.tsv.fi/julkaisufoorumi/haku.php?lang=en - it is curated by Finnish scientists. Level 0 journals are not up to the standards, for whatever reasons (e.g. lack of peer review, content is not scientifically interesting), while 1-3 qualify as scientific publications. The database also contains Danish and Norwegian journal levels, where levels 1 and 2 indicate a scientific journal. The level of a journal does not ensure the quality or correctness of the article, but it gives some evidence. Publisher likewise.
Note that it is often difficult to get a definitive answer on whether a source is reliable or not, but if there are too many worrying aspects, best find something else to cite. Also, senior colleagues are an invaluable help, but remember that they might have idiosyncratic opinions, so better ask several.
Citation Machine gives a list of questions to examine when using an unfamiliar book:
Source credibility can impact your grade. Here are questions to guide your evaluation process: Contributor/Author
Is the author well known and frequently published? Are there any reviews available for the author's work? How easy is it to find contact information for the author?Publisher
Is the publisher well known and well respected in the industry? Do they have a website? How selective is the publisher in determining what they publish? Are they also the main retailer for what they publish? Does their other content seem legitimate and credible?Currency
When was the source originally published? When was it last updated? Are you citing the latest version? If not, how does that affect your argument?Accuracy
Does the argument the author makes appear anywhere else? Is it backed up with data or other sources? Where does the information presented come from? Are there grammatical or spelling errors? Any dead links?Relevance
What is the tone of voice? Does it appeal more to an academic reader, or is it more casual? Would someone not familiar with the subject be able to understand the source's topic after reading it? What is the intended audience of the source? Is it similar or different from your intended audience?Bias
If the source is a website, does the site have ads? Do they affect the content? What is the purpose of the source? Is it to persuade or argue? To entertain or inform? What is the author's tone of voice? Do they seem to only present one side of the argument? How do they address the counter argument, if at all?Citations
Does the author give credit to sources where they received information and conducted research? Do the sources they used seem legitimate? What sources refer to the one you are using? Do those seem legitimate?Reproduced
Is this the original source? Has it been reproduced? If it was reproduced, when was that done? Who reproduced it? To what end? If it was reproduced, does it have copyright information or information on the original source?Complete
How much information can be learned from the source on a particular topic? Does it talk about a broad topic, or a specific element of a topic? Are there larger, more popular sources on the topic than this one?Credible
After reading through the various questions above, does this source seem credible?
How do I know if a book is sufficiently reliable to use as a source in my paper?
Ultimately, you don't know whether sources are reliable. This shouldn't cause a problem: You needn't rely on a single source. For instance, you can write statements such as, "Alice and Bob found ..., whereas Charlie ..."
