I just wondered what is the percent of people who rate a quiz. I have one quiz that has been played over 53 times without a rating. I know that a quiz must be rated 30 times before it has a rating. I just wondered what the usual number of plays that would be.

If I've understood your question correctly:
the avge user rating is not calculated by the system until a quiz has been online for 20 days; when it loses its "new" label and its ranking calculated (the site-wide ranking out of 65,000 odd quizzes). See this post by Terry: New Quiz Rankings Feb 04

I've scrolled through the Newest Quizzes list, and the cut-off pint is still 20 days.

Thank you. On page http://www.funtrivia.com/quizlist2.cfm?myquizzes=1&rank=yes
it indicated 30 ratings rather than 20 days.