# 7.06 Summary

• The precision of a measurement can be stated explicitly by clearly stating the uncertainty in the measurement.
• The precision can be implied more conveniently by the number of digits used when numbers are written in scientific notation. In this case the uncertainty is taken to be within +/- half a unit of the last digit
• More digits means more precision
• For measurements with the same number of digits, the number with largest first digit is more precise. (if the first digits are the same compare the second digit etc).
• When the uncertainty in a measurement is expressed explicitly there must be consistency between the number of digits used to record the nominal value and those used for uncertainty.
• When measurement values are used in calculations extra digits can be generated in the answers. These should not be included in the result as it would imply greater precision than was present in the original measurement values. (There are rules for determining how many digits should be included in the results of calculations- see later section)