# Measurement, Errors, Data and Unit Conversion

• Martin Caon
Chapter

## Abstract

All measurements involve a number, a unit and a level of uncertainty. The number is usually expressed in scientific notation (with a power of 10), while the units should be in metric units and be part of the standard international system (SI) of units. Examples are the metre, second, kilogram, ampere as well as derived units such as the litre, newton and pascal. However, sometimes the units that are commonly used are not SI and you should be aware of these. The metric units will have standard prefixes (kilo, milli, etc.) to denote known multiples of the standard unit. You should be able to convert between different prefixes of the same unit and to convert between one unit and another. No measurement of a continuous variable (like height, weight, temperature, blood pressure) is known with absolute accuracy, so its level of uncertainty is usually stated. Uncertainty is sometimes stated as the “error”, but this does not imply that a mistake has been made, just that the true value lies within a known upper and lower boundary.