The response rate (responses divided by unique pageviews) varies across different pages. And in fact the pages with low response rate also tend to have a higher ratio of negative ratings. This suggests to me that many users who don't find a page helpful just leave without rating it. (I have looked at other factors that could have affected response rate but the correlations are very weak.)

I understand that it's problematic to generalize the result for pages that have a low response rate. But I'm reluctant to exclude these pages, since it seems that they may be the ones most in need of attention. In view of this, is it reasonable to ignore response rate per page and simply look at the positive to negative ratings ratio? Or is there a way I could account for response rate and still include these pages?

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What is your mental model of decisions made by people visiting your site? Is there any difference between first-timers and people using your site regularly? Will regular visitors think of spending a second answering the question? Do you have any extra variables from analytics (Ggle's or others')? Non-response may be correlated with those variables... –  Deer Hunter Dec 22 '12 at 18:27
Thanks for the tips, Deer Hunter. Some interesting avenues to explore there. Currently I just have the general analytics, not directly linked to responses and response rates. For example, I can look at things like average time on page for the pages that got lower response rates (not much correlation for that one), but I don't have the specific time on page numbers for only those visitors who didn't respond. –  Joe Pairman Dec 23 '12 at 3:32