Who cares? Sig Figs measure the degree of precision of a measurement.
But first: What’s the difference between accuracy and precision? Do they mean the same thing?
Important definitions: accuracy: a measure of how closely a measurement agrees with the correct or true value precision: a measure of how closely individual measurements agree with one another
Example question: Two students measured the mass of a small pebble, which had an actual mass of 2.35 grams. Sally’s measurements were 2.78 grams, 2.82 grams, and 2.81 grams. Madison’s measurements were 2.30 grams, 2.34 grams, and 2.41 grams. Which student was more accurate? Which student was more precise?
A correctly precise measurement includes all digits that are known for sure, plus a digit that is estimated.
You and your lab partner, Sloppy Joe, have been assigned to find the area of your lab table. You carefully measure the length, and find it to be 233.65 cm. Sloppy Joe casually slides the meter stick along the width, suggests that it measures about 200 cm.
233.65 x 200 = 46730 5 S.F.1 S.F.4 S.F.? Answer must be recorded as 50,000 cm 2 It can have only one sig fig.
Your answer MUST have the same number of sig figs as the factor with the least number of sig figs.
610 x 6.20 = 3782 2 S.F.3 S.F. What is the correct answer? 3800
Example: You calculate the density of an object with mass of 24.300 grams, and volume of 62.5 ml. How many sig figs in your answer? D=M/V 24.300/62.5 = 0.3888 Correct Sig. Figs. = 0.389