Accuracy and Precision

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Jennifer Torres 2L
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Joined: Tue Nov 14, 2017 3:01 am

Accuracy and Precision

Postby Jennifer Torres 2L » Thu Oct 04, 2018 10:45 pm

Hey, I was wondering if someone could clearly explain the difference between Accuracy and precision in chemistry (lab setting) thanks!

Melissa Villanueva1K
Posts: 64
Joined: Wed Nov 15, 2017 3:01 am

Re: Accuracy and Precision

Postby Melissa Villanueva1K » Thu Oct 04, 2018 10:49 pm

Accuracy refers to the closeness of a measured value to a the desired or known value. While precision refers to the closeness of two or more measurements to each other. Take a look at the target examples that were shown in lecture for a better reference. Hoped it helped!

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Re: Accuracy and Precision

Postby kamalkolluri » Thu Oct 04, 2018 10:50 pm

Let's say you did an experiment trying to find out how much water is produced from a combustion reaction. And lets also say the actual value you should have gotten should be 1 Liter of water. So if you do your trials and you get 0.2L, 0.16L, 0.18L, and 0.22L, your data is precise because all of your trials resulted in numbers very close to each other. However, your data is not accurate because your measurements are not close to 1L. So precision simply depends on how far apart your data is and the accuracy depends on how far your data is from the actual value you should've gotten.

Lydia Luong 4L
Posts: 59
Joined: Fri Sep 28, 2018 12:24 am

Re: Accuracy and Precision

Postby Lydia Luong 4L » Thu Oct 04, 2018 11:06 pm

High accuracy is when your data results from your lab are close to the number that you were expecting to get from your prediction/calculation beforehand (how "right" your data results are,) even if your results only hit that "right" number only three times out of seven trials. High precision, however, means that your data results are all consistently the same or very similar to each other(basically, when you get the same results/numbers over and over again), even if they may not be anything close to what you were "supposed" to get. So, results with both high accuracy and high precision are both very close to the right value, and also consistent (you're landing near that number all the time.)

Tony Chung 2I
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: Accuracy and Precision

Postby Tony Chung 2I » Fri Oct 05, 2018 2:56 am

Picture an archer doing target practice. If the archer is relatively hitting the same spot on the target, that would be considered as precise. If the archer is constantly hitting the bullseye, that would be considered as accurate.

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