# Some Important Points

- A measurement of a physical quantity is said to be accurate if the systematic error in its measurement is relatively very low. On the other hand, the measurement of a physical quantity is said to be precise if the random error is small.
- Errors are always additive in nature.
- For greater accuracy, the quantity with higher power should have least error.
- Absolute error is not dimensionless quantity.
- Relative error is dimensionless quantity.
- Least count
- Least count of vernier callipers
*Ââ€“*1 - Least count of screw guaze
- Smaller the least count, higher is the accuracy of measurement.
- Larger the number of significant figures after the decimal in a measurement, higher is the accuracy of measurement.
- Significant figures do not change if we measure a physical quantity in different units.
- When we add or subtract two measured quantities, the absolute error in the final result is equal to the sum of the absolute errors in the measured quantities.
- When we multiply or divide two measured quantities, the relative error in the final result is equal to the sum of the relative errors in the measured quantities.