# Finding percentage uncertaintys

#### greener1993

I need help on how to work out uncertianity is there a set equation for it?

i found this on the web
Step 1:
Add up all your values and divide by the number of values

Step 2:
Subtract each value from this average value and take the absolute value from this (positive numbers)

Step 3:
Add up all these absolute values and divide by the number of values

Step 4:
Take this value and divide by the square root of the number of values you have

This 4 step process gives you the uncertainty of the data you have collected

is this correct?

1) when measuring wire i got the resualts of
0.28mm
0.28mm
0.28mm
0.29mm
0.29mm
0.29mm
0.28mm
0.29mm

The actual width of the wire said on the roll was 0.28mm and theses were taken with a electronic vernier scale which measures to 2dp of a mm. (if this is of any use)

i also read that if the uncertainity is below what the equipment can measure it is neglecable. And i also need to know how to turn it into a percentage