Answer and Explanation:
Credibility is very important when choosing a source because if you select wrongly, you could be reporting/writing about false information.
First, look at who the author of the source is. Usually, if they are well-known authors or organizations (for example, the World Health Organization or the United Nations), this will be a good source to use.
Next, check out the date the article or source was written. If it was written recently, there's a higher probability that it will apply better and lend more credibility than if it was written 10 years ago.
When using websites, take a look at the URL. Those that end in .gov and .edu are usually relatively trustworthy because they are created by trusted organizations. However, if you have a website that ends in .com or .org, make sure you check what organization it is because they're not always credible.
Finally, look at who the author intends to write for. Is the audience a group of teachers? Or is the article targeted to young children? Research scientists? Whichever audience the article pertains to, if it doesn't relate to your thesis and research, I advise you not to use it.
Hope this helps!