Sunday, October 23, 2016

Never work without a net: why units matter

I've been working on measurement and units in synthetic biology for more than five years now, so it would seem that I should have a pretty clear understanding of the landscape. As you, dear reader, may recall, for a long time I've been arguing in favor of getting independently calibrated units into our work in synthetic biology, and working on ways to make this generally accessible. Over the past 24 hours, however, I've come across something that has blown my mind.

The arguments for having units that you can compare across different experiments, devices, and laboratories have been pretty strong and clear, since yes, of course, we want to be able to compare our work.  Many people, however, believe that it's good enough to have relative units, where you measure in arbitrary units and then normalize your data by a known genetic construct control.  I have not been comfortable with this, because you have no way to know if something goes wrong that affects your control as well.

My arguments there, however, have always felt relatively weak, because: a) how do I know if this actually happens often enough to be a real concern? and b) it sounds like I'm accusing people of doing sloppy lab work, which would be doubly unfair since most scientists I know are quite careful and since I don't do any lab work at all.  So while I've had a clear argument against relative units that it persuasive to those who are already basically in agreement, I haven't really had a leg to stand on, scientifically speaking, in my concerns about relative units, and have sort of dismissed it down to a level of secondary concerns.

But in the data from this year's iGEM interlab, we have hard evidence that relative units are not enough, because having a way to catch the results of those little mistakes really matters. I can't give you any more details for a week, not until after we officially unveil the results next week at this year's iGEM Jamboree, but it's a big deal.  Like, orders of magnitude big deal.

My world is rocked.  It's obvious in retrospect, and I've even made the argument before. There's a difference, however, between making an argument and having data staring you in the face that says that the argument is far more important than you ever had actually realized.

Basically, if you're not using units, then you're working without a net. With units, you have a chance to apply a bit of experience and common sense and realize that something is going wrong with your numbers. You might not know how or why, but usually that's not actually important, because usually it's something small and stupid (dropped a minus sign, got left and right mixed up, grabbed the wrong bottle, etc.), and the best way to fix your mistake is just to do it again, because you probably won't make the same stupid mistake twice in a row. This applies to pretty much everything in life involving numbers and measurements, not just to biological research.  Using properly calibrated units gives you a second chance to notice your mistake, and makes all the difference between embarrassment and disaster.

How big a difference, exactly? Well, I'll just go grab a cake to celebrate and I'll see you in about a week.
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