Measurements in Science is the process of obtaining the magnitude of a physical quantity and expressing it relative to a certain basic, arbitrarily chosen, internationally accepted reference standard called UNIT.
We need only a limited number of units to express all the physical quantities because these quantities are dependent on each other. We assign a set for fundamental or base quantities only, the units for these are called the Fundamental/Base units.
All remaining quantities can be derived from the base quantities. The units for these derived quantities are called derived units.
A system of units = Fundamental Units + Derived Units
There are different systems of units e.g. CGS(centimeter, gram and second), MKS(meter, gram and second) etc. However, the most commonly used standard is the SI system.
7 Base quantities
|Amount of substance||mole||mol|
2 additional quantities
Degree of uncertainty associated with a measurement.
Result = measured value ± absolute error
Accuracy is a measure of how close the measured value is to the true value of a quantity.
Precision tells us to what resolution or limit the quantity is measured.