Lesson 3: Significant Digits
Scientists take the ideas of precision and accuracy very seriously.
•
You can actually take entire courses in University that show how to figure out the precision and
accuracy of measurements.
•
Guess what? I took 'em!... your opinion of me has probably slipped a few notches ; )
•
We need to know that when another scientist reports a finding to us, we can trust the accuracy and
precision of all the measurements that have been done.
•
A set of guidelines is needed while we do calculations so that we get rid of all those
“
4.243956528452940472
” kind of answers you see on your calculator.
•
The guidelines are there so we will know how many digits we should round off the final answer
to show the correct precision.
All of this boils down to something called “
Significant Digits
”, more commonly referred to as
Sig Digs
.
To determine how many significant (
important
) digits a number has, follow these rules:
1.
The numbers 1 to 9 are
always
sig digs. Zero ("0") is a sig dig if it comes to the right of a number
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 Spring '09
 Knott
 Physics, Accuracy and precision, sig digs

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