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What's the difference between accuracy and precision?

Added Jun 09, 2017 •

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as The Story Goes the legendary Marksman singtel was forced into a cruel challenge by a corrupt Lord William son was to be executed unless William could shoot an app off his head William succeeded but let's imagine two variations on the tail in the first ameri ation the Lord hires a band to steal Williams trustee crossbow so he is forced to borrow an inferior one from a peasant however the borrowed crossbow isn't Justin perfectly and William finds that his practice shots cluster in a tight spread beneath the bullseye fortunately he has time to correct before it's too late variation to William begins to doubt his skills in the long hours before the challenge and his hand a Tremor is practice shots still cluster around the Apple but in a random pattern occasionally he hits the Apple but with the wobble where is no guarantee of a bullseye he must settle his nervous hand and restore the certainty in his aim to save his son  at the heart of these variations are two terms often used interchangeably accuracy and precision the distinction between the two is actually critical for many intific Endeavors accuracy involves how close you come to the correct result your accuracy improves with tools that are calibrated correctly set your well-trained on Precision on the other hand is how consistently you can get that result using the same method your Precision improves more finely incremented tools that require less estimation the story of the stolen crossbow was one of precision without accuracy William the same wrong result each time he fired the variation with the shaky hand was one of accuracy without Precision Williams bolts clustered around when do the correct result but without certainty of a bull's-eye for any given shot you can probably get away with low accuracy or low Precision in every play tasks but engineers and researchers often require accuracy on microscopic levels with a high certainty of being right every time factories in Labs increase Precision through better equipment and more detailed procedures these improvements can be expensive so managers must decide what the acceptable uncertainty for each project is however investments in Precision can take us beyond what was previously possible even as far smart it may surprise you that NASA does not know exactly where their probes are going to touch down on another planet predicting where they will land requires extensive calculations fed by measurements that don't always have a precise answer how does the Martian atmosphere density change at elevations what angle will the probe hit the atmosphere at what will be the speed of the probe upon entry computer simulators run thousands of different land scenarios mixing and matching values for all of the variables weighing all the possibilities the computer spits out the potential area of impact in form of a landing ellipse in 1976 The Landing ellipse for the Mars Viking Lander was 62 x 100 84 miles nearly the area of New Jersey with such a limitation NASA had to ignore many interesting but risky Landing since then new information about the Martian atmosphere improved spacecraft technology and more powerful computer simulations have dress likely reduced uncertainty in 2012 The Landing ellipse for the Curiosity Lander was only four miles wide by 12 miles long an area more than two hundred times smaller than Vikings this allowed NASA to Target a specific spot in Gale crater a previously on turn the pool area of high scientific interest while we altimate Lee strive for accuracy precision reflects our certainty of reliably achieving with these two principles in mind we can shoot for the stars and be confident of hitting them every time

Uploaded by Michelle Martin.

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What's the difference between accuracy and precision?

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