How do you calculate linearity?

Calculation of Linearity

Linearity refers to the degree to which the plotted points in a graph (representing the relationship between an instrument's output and its input) form a straight line, and thus it measures the fidelity of the input to the output over a range of values.

Calculating linearity involves comparing the measured values from an instrument or system across its entire operational range against a reference standard. The process can be abstracted into the following steps:

  1. Identify the full operational range of the device or system to be tested.
  2. Divide this range into a series of specific points at which measurements will be taken.
  3. Use a reference standard to measure the true values at these specific points. The reference should be more accurate than the device being tested.
  4. At the same specified points, measure the values using the device or system under test.
  5. Plot these measurements on a graph, with the reference values on the x-axis and the corresponding system/device measurements on the y-axis.
  6. The ideal result is a straight line (y = x), indicating perfect linearity.

Quantitative Assessment:

To quantitatively assess linearity, the deviations from the ideal straight-line response (linear regression line) are calculated. This can be done using statistical methods such as calculating the correlation coefficient (R-squared value) or conducting a linearity analysis through ANOVA for a more detailed assessment.


Linearity calculation provides crucial insight into the accuracy and reliability of measurement systems and instruments across their operational scope. By understanding the linearity, engineers and scientists can ensure the precision of their instruments and make adjustments or corrections to improve measurement accuracy.

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