Science! // Let’s Talk Precision and Accuracy.

Happy Fourth of July to all my friends in the states! And happy Monday to all my international friends! Today I’m introducing a brand new series/tag: Science! (with the exclamation point). My goal is to make every Monday a Science! day. In this tag I’ll be talking about various scientific principles and sharing with you my own little “science” experiments. Some days will be about concepts, some scientific and some from other STEM fields, and some days will be about data- and a lot of it will be related to health and beauty. This week is a topic that I think I need to talk about before I can get into any data: precision and accuracy in measurements.

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For those who don’t know, my education background is rooted in math and science. I lapped up the chance to learn algebra when I was very young. I was the kid who competed as a mathlete from the age of 8 or 9, the kid who excelled in biology and chemistry, and my degree is actually in biology, with minors in chemistry and psychology. I am a member of the AAAS and my favorite magazines are Science (which is more of a journal) and Science News (which is more for fun). My point is this: I’m well versed in scientific matters, and I prefer to test things out scientifically when possible.

I became incredibly excited when I found out about BIA “skin moisture” analysis devices. I figured this was the perfect way to show the efficacy of routines and sheet masks. While I have no way of determining the accuracy of the device, I can talk to you about the precision and give you some preliminary results, which I’m gonna do… next post.

For now let’s talk about precision vs accuracy.  If you have a good grasp on the difference, feel free to skip this post… However, this is going to be a very informative post. I find it easiest to explain precision and accuracy with images, so let me explain the difference with a cute infographic!

Precision vs.Accuracy.png

For my math friends, we can relate precision and accuracy to statistics. Accuracy is like the average and precision is like a standard deviation. The closer the average is to “true value,” the more accurate a measuring instrument is. The smaller the standard deviation (relative to value), the more precise it is.

Most instruments we use in day to day life are moderately accurate and precise. A measuring cup when you are cooking dinner will always hold pretty close the same volume (provided you use it the same). Scales don’t change drastically when we step on them a second time. Accuracy is something we just believe, most of the time, but usually manufacturers design and calibrate their instruments to be accurate. That said, we often find little problems. Commonly, one scale weighs you a pound heavier than another (ever been to the doctor’s?) or we know that our measuring cups run a bit larger or smaller. We often adjust for this accuracy ourselves, either in your minds subtracting that extra pound or adding the extra tablespoon of flour to our recipes.

I know that was a lot of info, but it’s super important to understand the limitations of instruments I use to get a good feel on a product. In my next Science! post next week, I’m going to talk to you about the accuracy and precision of my cool new moisture monitor and give you my “baseline” values for July (data was taken on June 30th). If you have any questions, please leave a comment for me! Let me know if this was helpful and if there are any scientific concepts you’d like me to touch on in the future.

Stay curious!
– Lucy

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