Choosing appropriate words for lay summary of a health research project
Ways of finding out whether the words and phrases you use in a lay summary are appropriate to the public audience:

One approach is to put your text into something like simplewriter.

http://xkcd.com/simplewriter/

It highlights words which are not part of the most commonly used 1000 words in English. 

That specific program is a little bit limited, more for an audience of children but there are similar text editors which can highlight complex or rare terms. 

If you limit it to the 20000 most commonly used english words things should be readable by most laypersons.