Re: BQL values, version 3

Date: Mon, 2 Aug 1999 16:57:06 +0100 (GMT) From: "J.G. Wright" <J.G.Wright@newcastle.ac.uk> Subject: Re: BQL values, version 3 Dear Lew, Of course, you are right about the definition of the likelihood. My phrasing was unfortunate, what I meant to emphasize was that was that BQL observations can come from true values above the range and fixing BQL observations to BQL/2 with symmetric error doesn't seem appropriate to me. I misused the term "support" to mean weighted true values consistent with the observation. This indeed what you have to consider when imputing values. I believe the word support in your explanation means the relative weighting of possible observations consistent with the observed value. My point about substituting data values providing narrower confidence intervals is, I believe correct, and i don't think "inflating" residual error (downweighting the BQL observations) correctly compensates for this. Indeed, it may introduce some degree of bias. Of course, if you are going to integrate over the possible observed values below QL, this is not an issue as you are not imputing a fixed value. In the implementation of the integration approach however what distribution (ie support) do you assume for the observations below BQL (eg uniform, lognormal etc)? This remains an assumption which is critical to the analysis, whatever method you use. James