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Accuracy is exactly the same thing as precision.

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Oops. That sentence was neither accurate nor precise.

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So wait a minute. What are we doing wrong here?

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Are we taking two terms that mean different things and just assuming they mean the same thing?

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Since both are concepts we want to adhere to when conducting experiments...

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...we should probably make sure we've got our heads properly wrapped around them.

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First things first: what is accuracy?

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Well, let's say you're potty training your new cat.

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Whisker pees 5 times the first day...

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...he's drinking plenty of water.

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The goal, obviously, is for her to pee into the litter box.

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Not onto your pillow.

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Nobody said potty training was easy.

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Only one pee out of five hits the desired target.

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The other four are going to make your carpet and pillow smell funny for at least a month.

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The second week, Whiskers is hitting the litter box three out of five times.

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By the end of the month, all five attempts hit their mark.

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Well, this is an example of accuracy.

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At the beginning, Whiskers was exceedingly inaccurate...

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but over time, her accuracy improved.

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All right. Now, what about precision? Let's go back to that first week.

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Only one attempt made its way into the litter box, but check out that grouping.

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Well, even though Whiskers did an awful job of using the box...

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she sure was consistent.

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Fast forward a couple weeks, and the pees are bit more spread out.

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Finally, whiskers is getting every pee into the box, but they're more spread out than ever.

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Here we seen an example of precision.

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Whiskers starts out by being very precise; i.e., all the pees are within two inches of each other...

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...and winds up being very imprecise; i.e., her pees are all over the place.

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So, something can be accurate and imprecise...

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...or inaccurate and precise.

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Now we can apply this concept to an actual scientific experiment.

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Suppose you've hypothesized that mixing two chemicals will cause the mixture to heat up to 80 degrees Fahrenheit.

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If you perform the experiment five times, and every time, the mixture does, in fact, heat up to 80 degrees...

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...then your results are both accurate and precise.

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But if every time you take a measurement, you instead get 62 degrees...

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...well, then your results are precise, but not at all accurate.

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If our five results come back as 75, 78, 82, and 85 degrees...

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...well, our results seem pretty accurate, but they leave something to be desired in the precision department.

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We drew a pretty cool graph to demonstrate this stuff, but...

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...well, we foolishly left it next to Whiskers' litter box.

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Yeah, we love you too, Whiskers.

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