Measuring Instruments and Errors

Error and Uncertainties

Junior College 1

Learning outcomes

• Understand effect of systematic errors and random error in measurement

• Differentiate between precision and accuracy

• Absolute or relatives uncertainties

• Significant figure expression

Measurement error

Measurement Error (also called Observational Error) is the difference between a measured quantity and its true value. It includes random error (naturally occurring errors that are to be expected with any experiment) and systematic error (caused by a miscalibrated instrument that affects all measurements).

Accuracy Vs Precision

The differentiation and the importance

The importance of

• Accuracy represents how close a measurement comes to its true (standard) value. This is important because bad equipment, poor data processing or human error can lead to inaccurate results that are not very close to the truth.

• Precision refers to how closely individual measurements agree with each other.

Significant Figure

Number of digits in a value which contributes the level of accuracy of the value is called significant figures. The number of significant figures expresses the precision of a calculated value by a scientist or an engineer.

Rules of significant figure