She’s right to be worried! There are so many possible cracks that bias can seep through, nudging clinical trial results off course. Some of the biggest come from people knowing which comparison group a participant will be, or has been, in. Allocation concealment and blinding are strategies to reduce this risk.

Before we get to that, let’s look at the source of the problems we’re aiming at here: people! They bring subjectivity to the mix, even if they are committed to the trial – and not everyone who plays a role will be supportive, anyway. On top of that, randomizing people – leaving their fate to pure chance – can be the rational and absolutely vital thing to do. But it’s also “anathema to the human spirit”, so it can be awfully hard to play totally by the rules.
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And we’re counting on a lot of people here, aren’t we? There are the ones who enter an individual into one of the comparison groups in the trial. There are those individual participants themselves, and the ones dealing with them during the trial – healthcare practitioners who treat them, for example. And then there are the people measuring outcomes – like looking at an x-ray and deciding if it’s showing improvement or not.
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