Skip to main content

More than one kind of self-control


If you like reading randomized trials about skin and oral health treatments - and who doesn't? - you come across a few split-face and split-mouth ones. Instead of randomizing groups of people to different interventions so that a group of people can be a control group (parallel trials), sections of a person are randomized.

It's not only done with faces and teeth. Pairs of body parts can be randomized too, like arms or legs. These studies are sometimes called "within-person" trials. This kind of randomization means that you need fewer people in the trial, because you don't have to account for all the variations between human beings.

It has to be a treatment that affects only the specific area of the body treated, though. Anything that could have an influence on the "control" part is called a spill-over effect. There are still inevitably things that happen that affect the whole person, and those have to be accounted for with this kind of trial. Body part randomization is one of several ways a person can be their own control: the n of 1 trial is another way.

Randomizing sections didn't start in trials with people: it began with split-plot experiments in agricultural research. The idea was developed by the pioneer statistician, Sir Ronald Aylmer Fisher, who had done breeding experiments. He explained the technique in his classic 1925 text, "Statistical Methods for Research Workers."

It's great to see that neither blackheads nor treatment effects are hampering the Twilling sisters' style! They do seem to be at risk of susceptibility to the skincare industry's hard sells, though. Those issues are the subject of my post Blemish: The Truth About Blackheads.


Comments

Popular posts from this blog

Austerity-A Fancy Word for Destitute.

The reason for this post is not for the folks who have been caught in the first wave of personal economic hard reality, but the next wave. Regardless of the optimism espoused by grinning leaders and sycophant press, we are entering the final stage of global economic collapse. It began in 2008 and was forestalled for five years with fudge putty, but the weight of global indebtedness cannot be propped any longer and the final crunch is imminent. Austerity measures herald the final throes.  Indications of coming austerity.   Austerity measures are the final last ditch effort, futile or not! Back in the day many of us old-timers went through periods of "hard-times". In retrospect I realize there is no comparison to yesteryear hard times and today's version. Back then, expectations were never very high for the working class, there were no sophisticated systems or conveniences anyway. In fact the difference between being "set" or not was about having treats or not. Si...

Terrifying Arctic methane levels

A peak methane level of 3026 ppb was recorded by the MetOp-B satellite at 469 mb on December 11, 2021 am. This follows a peak methane level of  3644 ppb  recorded by the MetOp-B satellite at 367 mb on November 21, 2021, pm. A peak methane level of 2716 ppb was recorded by the MetOp-B satellite at 586 mb on December 11, 2021, pm, as above image shows. This image is possibly even more terrifying than the image at the top, as above image shows that at 586 mb, i.e. much closer to sea level, almost all methane shows up over sea, rather than over land, supporting the possibility of large methane eruptions from the seafloor, especially in the Arctic.  Also, the image was recorded later than the image at the top with the 3026 ppb peak, indicating that even more methane may be on the way. This appears to be confirmed by the Copernicus forecast for December 12, 2021, 03 UTC, as illustrated by the image below, which shows methane at 500 hPa (equivalent to 500 mb). Furthermore, ...

Women and children overboard

It's the  Catch-22  of clinical trials: to protect pregnant women and children from the risks of untested drugs....we don't test drugs adequately for them. In the last few decades , we've been more concerned about the harms of research than of inadequately tested treatments for everyone, in fact. But for "vulnerable populations,"  like pregnant women and children, the default was to exclude them. And just in case any women might be, or might become, pregnant, it was often easier just to exclude us all from trials. It got so bad, that by the late 1990s, the FDA realized regulations and more for pregnant women - and women generally - had to change. The NIH (National Institutes of Health) took action too. And so few drugs had enough safety and efficacy information for children that, even in official circles, children were being called "therapeutic orphans."  Action began on that, too. There is still a long way to go. But this month there was a sign that ...