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What Do These Commonly-Used Words Really Mean?

Today is World Dictionary Day, and in honor of that I’d like to discuss a few words that are used a lot in our conservation science work.  They are: Precision, Accuracy, and Bias.  These may seem familiar, but they have important definitions when used in a scientific setting.  When we measure things – say, the number of trees in an area slated for restoration, or the size of the individual fronds on a fern, we need to know how well we measure them.  If our measurements are no good, it means that our answers are probably no good as well.  Science is at its heart the search for truth, and measurements are the tools we use to find that truth.

Precision and Accuracy are often used interchangeably, but there is an important difference. Accuracy tells us how close our measurements are to the truth; while Precision tells us how close our measurements are to one another.  It is possible to be accurate but not precise, just as it is possible to be precise but not accurate.

Image source: practicalanalyst.com
Image source: practicalanalyst.com

Bias means that there is an error in our measurement system that causes the results to be wrong in the same way.  For example, if we are measuring the height of a tree (like last week) and forget to include our own height in the measurement, we will have a bias toward too small a measurement.

When we design research studies, or test the effectiveness of our restoration treatments, these three words help define how we work.  How accurate do we need to be?  How much precision is important?  Can we allow some bias if we understand and account for it?  Each project is different, but the principles remain the same.

Have a question about a redwoods-related word? Leave us a comment and we’ll do our best to get you that definition! Or, check out the glossary of terms from our recent Redwoods and Climate Change Symposium.


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About Richard Campbell

Richard joined the League’s staff in 2012 as the Conservation Science Manager. He brings nearly a decade of experience in forest management and restoration.



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