Chapter 1 Part 2 Precision, accuracy And significant figures Measurement Chapter 1 Part 2 Precision, accuracy And significant figures

Precision Precision is a measure of how well an instrument can measure if used correctly under good conditions. Examples: A car Odometer is precise to the nearest tenth of a mile. A meter stick is precise to the nearest half millimeter

Accuracy Accuracy is a measure of how well a person using an instrument makes a specific measure. Accuracy is limited by: the precision of the instrument, the conditions under which the measure is made The person, his/her actions & perceptions

Accuracy and Significant Figures The Convention of “Significant Figures” allows us to express the level of accuracy honestly. A measure written 4.4 m is accurate to the nearest decimeter (1/10th a meter). That is it might really be 4.41 m or 4.38 m but it is not 4.48 m or 4.5 m If you write 4.40m you are claiming that your more accurate… To the nearest centimeter!

Rules for Significant Figures Non Zero numbers are always significant Zeros between nonzero numbers are always significant Final Zeroes to the right of the decimal are always significant Place holder zeros are not significant…to eliminate them use scientific notation Counting numbers and defined constants have an infinite number of significant figures

Calculations and Sig-fig Calculations can make it seem that our answers are more (or less) accurate than they really are. Thus we have rules for calculating with sig-fig. Addition/Subtraction Round your answer to the last digit of your least accurate measure Multiplcation/Division Round your answer to the least number of sig-figs in your measures (Copy Examples)