UCL vs UTL in the results vs. lognormal density graph


The numerical results on the top left show the 95th percentile and 70 and 95 UCLs. On the lognormal density curve however, the displayed name for these UCL is UTL. Its is not untrue, but it might be better to be consistent, which begs the question : should we use UTL or UCL ?

Personnally I would stick with UCL, and maybe state somewhere in the help file that both concepts are equivalent. Any opinion ?

The data boxes list the values as UCL70 and UCL95, EN689 talks about UCL70, in Australia we use UCL95, which are the x% confidence limits of the point estimate of the AM. My understanding of the UTL95,95 (as applied in OH) is that it is the 95% upper limit of the 95%ile, in which case they are different in their interpretation in the OH field. In my experience UTL95,95 is not generally employed as a measure of exposure risk, despite being in IHSTATS. The UCL95 or point estimate of the 95th%ile is used. I also believe that for many hygienists the UTL95,95 is a difficult concept. Most simply take the IHSTATS Lands UCL and compare that to the WES.

I support sticking with UCL, for now. As statistical fluency increases perhaps including these additional parameters might be useful, but it does need to be related back to exposure risk and if its not better than our other measures then its value might not be sufficient to warrant adding it in.