🚀 go-pugleaf

I have some questionnaire data from which I wish to derive a "knowledge
index"   by taking the mean response to several of the questions. 
However, these are true-false questions and more of the questions are
true than false.  Moreover, many people are clearly disposed to choose
True as a response rather than False.  Of course, to the degree that
they have this bias their knowledge index is inflated.

I have solved this problem by taking the (unweighted) mean of the mean
answer to false questions plus the mean answer to true questions.

My question:  can you think of anything wrong with doing this?  

BTW, I realize that taking the "mean" of ordinal responses is
problematic, but I'm willing to weather this storm on my own -- which
doesn't mean that I am uninterested in comments on that issue.

Thanks in advance,

daniel