## Accuracy and Precision

so what is the difference between

accuracy and precision what do you think

the difference is accuracy has to deal

with the idea of how your data matches

up with the true data so the closer your

data is to an accepted value the more

accurate your data is precision has to

do with if your data agrees with each

other so if your individual measurements

are in agreement with each other then

your data is precise so accuracy has to

do with how close your data is with the

accepted value and precision is how

close your data is with each other so

let's try this problem so this can help

you to see the difference between

accuracy and precision for students

performed an experiment to measure the

density of aluminum and the accepted

value for that is 2.7 grams per

milliliter now let's say that the data

here represents the same units which

data is accurate but not precise let's

focus on accuracy let's start with John

it since beta is it accurate or is it

precise I mean is it accurate or is it

not now 2.9 is not very close to 2.7 so

his data is not accurate so I'm going to

put an A for not accurate

now what about Sally's data is it

accurate is they close to 2.7 as you can

see the numbers they vary widely they're

not close to 2.7 at all so her data is

not accurate now what about Megan is her

data accurate now relative to John and

Sally

Megan's data is pretty close to two

point seven two point six four nine two

point seven three two point six nine

five that's very close to two point

seven so we can say that her data is

fairly accurate at least compared to

John's

stylish data now what about Mike Mike

state is definitely ad for it it's very

close to 2.7 now let's see whose data is

precise so let's talk about John's data

is it precise do the values agree with

each other and it turns out they do all

of these values each of his trials is

around two point nine two point nine two

four two point nine two three so those

numbers they're very close to each other

they agree with each other so John's

data it's precise now what about Sally

Sally's data is not precise

first it's two point three then it's two

point five then it's two point nine

those numbers do not agree with each

other they're not close to each other so

it's not precise and Megan is her data

precise her data jumps around to kind of

like Sally's Minnie not as Extreme as

Sally's data but it's not it doesn't

agree with each other the first is two

point six five then is two point seven

three then two point six nine five so

it's not very precise now Mike's data is

precise two point seven zero one and two

point six nine nine that's very very

close I mean the difference between the

trials are about maybe point zero zero

two or three so that that's very close

with jobs data it differs by point zero

zero one Megan's data third numbers

differ by many point zero five on

average so the lower the difference

between the trials that each data the

more precise it is so Mike's data is

precise so we're looking for the student

whose data is accurate but not precise

so that would be Megan so hopefully this

problem

helps you to see the difference between

accuracy and precision so keep this in

mind accuracy has to do with how close

your numbers are to the accepted value

Meghan and Mike's data are accurate

because these numbers they're very close

to two point seven precision has to do

with how close your data agrees with

each other

so John's data is precise because these

numbers are very close to each other and

Mike's data is precise as well because

those numbers are very close to each

other so now you understand the

difference between accuracy and

precision thanks for watching