Measurement: significant figures, accuracy, and precision

Every measurement has some uncertainty, so scientists report it with the right number of significant figures: all the digits known for certain plus one estimated digit. Reading a ruler marked in millimeters, you might record 12.3 mm, estimating the last digit. Nonzero digits are always significant; zeros between nonzero digits are significant (1,007 has four); leading zeros are not (0.0045 has two); and trailing zeros after a decimal point are (2.50 has three). When multiplying or dividing, round the answer to the fewest significant figures in any of the measurements; when adding or subtracting, round to the fewest decimal places. Accuracy is how close a measurement is to the true value, while precision is how close repeated measurements are to each other: darts clustered tightly together but far from the bullseye are precise but not accurate. Chemists use SI units, such as meters, kilograms, seconds, kelvins, and moles, and scientific notation, such as 6.02 x 10^23, to write very large and very small numbers clearly. They convert units with dimensional analysis, multiplying by conversion factors so that unwanted units cancel out.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report