Hello Everyone, we noticed that a large portion of you guys watch our videos without subscribing,
soooo…
what’s stopping you, click here to stay updated with our latest nerdy content!
Anndd… back to the video.
Assalamu alaikom, welcome back to another ATP video, wherein we’ll be explaining Precision
and Accuracy.
Let’s start with precision: Precision AKA “reliability” helps tell
us how close the results of a certain test are to each other.
For example, let’s say we have a faulty weighing machine.
If you step on it once and record say 72 Kg, if you step on it again and get 71 Kg, and
then again to get 73 Kg, notice how all these results are very close to reach other.
In other words, you can rely on this device to measure your weight because it is highly
precise.
If it was spitting out 72 Kg, 59 Kg, and 87 Kg, well, these numbers are all over the place,
so it’s not that reliable, not that precise.
You might’ve noticed in the first example that even though the numbers are close to
each other, they’re not exact.
Well, that’s because there’s usually a certain amount of random error that could
play a role.
If you minimize random error, you’re more likely to achieve a more precise test than
before.
Accuracy AKA “validity” is slightly different.
In addition to the weighing machine we had in the previous example, suppose we had a
standardized weighing machine next to it to see if we’re really measuring what we’re
supposed to measure.
In other words, is our weighing machine valid when compared to the standardized weighed
machine.
To understand this better, let’s label them to not confuse ourselves, weighing machine
#1 is the weighing machine in the previous example that gave you 72 Kg, 71 Kg, and 73
Kg.
Weighing machine #2 is another weighing machine that we will use for the same person.
Now as a fact, we now that this person’s weight is 82 Kg.
If you stepped on Machine #2 and it gave you 82Kg, well, that means two things:
Machine #1 was not close to the standard, so it is NOT valid, NOT accurate, so it IS
NOT measuring what it’s supposed to be measuring.
2- Machine number 2 is ACCURATE AND VALID, since it accurately measured the weight of
the person.
Validity decreases with increasing systematic error.
That is to say that if we tampered weighting machine number 2 to add 10 Kg to the every
result, every single final result would be systematically increased by 10 Kg, thus making
it less accurate as it’s not really measuring what it’s supposed to measure.
To help illustrate this example, s we measure the weight of someone who in reality is 60
Kg.
Weighing machine A and B will be used in this example.
A is valid and will be reasonably close while B is invalid and will shoot approximately
10 kg higher.
A gave us 58 kg, 60 kg, and 62 kg, while B gave us 68 kg, 70 kg, and 72 kg.
Notice how both weighing machines are still EQUALLY RANDOM so random error doesn’t really
explain why the machine is invalid, instead, it’s the systematic error of adding 10 kg
to weighing machine B which explains it.
To summarize, let’s go through this figure to illustrate the concept from another angle.
In the first figure, notice how the points are clumped together, therefore they are precise,
and notice how they all are averaging towards the middle of the archery board, therefore,
it is also accurate.
In this second figure, notice how the points are still clumped together, therefore they
are precise, but look at how they all are averaging towards the periphery of the archery
board, therefore, it is not accurate.
In the third figure, notice how the points are widely spread apart, therefore they are
not precise, but look at how they are averaging towards the center of the archery board, therefore,
it is accurate.
Lastly, in the fourth figure, notice how the points are widely spread apart, therefore
they are not precise, and notice at how they are averaging towards the periphery of the
archery board, therefore, it is also not accurate.
And that’s it, we hope you are now more precise and accurate after watching this video
And as always, don’t forget to like and subscribe to receive our latest explanations!