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Simple Samples: Part I

Posted by Stephanie A. Smith, Ph.D., on Thu, Nov 21, 2013 @ 10:00 AM

“Simple Simon went a-fishing, For to catch a whale; All the water he had got, Was in his mother’s pail.”

“Simple Simon went a-fishing,
For to catch a whale;
All the water he had got,
Was in his mother’s pail.”

Looking at it 40 years after the first time I probably heard it, Mother Goose’s Simple Simon now seems really bizarre.  I stumbled upon it during a Google-search-turned-complete-waste-of-time, and wondered if today’s more sensitized consumers of children’s literature bristle at the term “simple,” used to describe our mentally challenged protagonist.  The excerpt above struck me as a tool to bring up another bristly topic:  how to take a sample if you want to measure cyanobacterial toxins in a lake or reservoir impacted by a harmful algal bloom (HAB).

You see, what Simple Simon has is a sampling problem, much like what we have when trying to assess the toxins in a HAB-affected lake.  Simple Simon might conclude that “there are no whales in the water, because I looked all day and didn’t find any.”  If this came out on the local newscast of the day, “Simple Simon & Friends,” people might accept that conclusion, because he is after all an authority of sorts since he has his own newscast.  Hopefully someone in the audience would ask the question, “Well, how did he look for them?  When did he look for them?  Where did he look for them?”

Looking for something of interest, and trying to understand how much or how little of it there is in the context of space or time, requires sampling.  And that’s because you can’t typically count all of the items of interest, for all time, in all places where they might be found.  It seems obvious that Simple Simon overreached with his conclusion, because he did a very poor job of looking in the right place at the right time for whales.  However, unless Simple Simon could actually count all the existing whales, in all the oceans, for that particular day, he couldn’t really know how many exist.  Scientists couldn’t do that either, though, so they create agreed-upon methods to count a subset, or sampling of whales, and they try to draw conclusions based on how they sampled the whale population as a whole.  Sampling is never clear-cut, and unlike the case of Simple Simon, it’s not always obvious when someone has done a poor job of sampling.  Poor conclusions may be drawn, or worse yet accepted, if someone isn’t asking questions about how the samples were taken, for any experiment.

 

Thus for this first of three blog installments called Simple Samples, I am asking you, the reader, to consider this question:  How should I sample a lake to determine if there are toxins in it?  We’ll explore that question together in two more blogs, and I hope folks offer comments and feedback.  Meanwhile, I’m going to ponder what the heck Simple Simon was doing with that plum.

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