Debbie Knight

To err is … biological

In observation on November 29, 2011 at 2:22 pm

A little graphic humor: the error bar (source unknown)

Ah, the error bar.

It can tell us quite a bit about the results of an experiment.

Last week, my lab (a biology lab) had its weekly meeting with the chemists with whom we collaborate. When our graduate student mentioned that she would be setting up each experimental condition in quadruplicate, the chemists seemed a bit surprised.

Now, I don’t know about chemistry experiments, but I do know that when you are working with a biological system (whether it is cultured cell, an animal study, or a human clinical trial), there can be quite a bit of variability. This is why biologists need to repeat each experimental condition, to reduce the effect of that variability. When the results are averaged together, we also determine how much each of those data points is different from that average – which gives the error bar. If that error bar is long, then we know that there is quite a bit of “bounce” in the measurements. Ideally, the measurements would be nearly identical and the error bar’s length short.

But I’ve found that biology is rarely “ideal.”

As it turned out, it was a good thing we performed the experiment in quadruplicate because some conditions had long error bars – which suggested a trend in the data and pointed us in another direction.

I suspect that in the chemistry world (at least in our collaborator’s world), experiments give more precise results than they do in the biology world and that replicates aren’t as critical.

Sometimes I wish that were the case in the experiments I do.

But sometimes that’s where the truly interesting findings are found – in the “bounce” of an error bar.

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