Hello shorthouse,
I assume you're talking about
[[this project]]?
Some good starting hypotheses might include ones about the frequencies of certain letters or words. Would you expect 'e' or 'o' to show up the most often? Is 'and' used more commonly than 'the'? You could even link this to a more complicated idea if time allows. For example, I've often heard it said that 'ivy' is the hardest Hangman word, and definitely harder than 'and' or 'the'. Based on the relative frequencies of those letters, does that seem to be true?
Looking at the project idea, though, if your son doesn't have much experience with programming (and you haven't already started), I might recommend an alternative approach. JavaScript can be a little confusing, and the project appears to assume that you already have some knowledge of HTML. However, there are simpler and more straightforward ways to do the project. One such way is to use simple Java, which is usually one of the first languages taught to programming students, and .txt files, which are easily accessible with programming. It has several easy-to-use developing environments such as Eclipse and NetBeans.
Some Google searches for ".text analysis with Java", "text analysis with Java", and "word count with Java" might turn up some interesting examples, tutorials, and the like. I'd also recommend, if you decide to do this project, that you look at the
[[Javadoc]], as it's enormously helpful.
I hope this helped, and if you have more questions, feel free to ask!