Types of Uncertainty

What are the types of Uncertainty?

1. Absolute Uncertainty

2. Percentage Uncertainty

Absolute Uncertainty

uncertainty associated with a given value with the same units as the value its associated with

Percentage Uncertainty

absolute uncertainty expressed as a percentage of the value it’s associated with

Percentage Uncertainty Equation

absolute uncertainty/measured value * 100%

Relative/Fractional Uncertainty

ratio comparing magnitude of absolute uncertainty to the magnitude of the associated value

Relative Uncertainty

absolute uncertainty/measured value

What has to be done when multiplying or dividing?

the answer must be quoted to the same number of sig figs as least precise data (lowest number of sig figs)

What has to be done when adding or subtracting?

the answer must be quoted to the same number of decimal places as least precise data (lowest number of decimal places)

What must be done when adding or subtracting measurements (in terms of propagation)?

the uncertainty in the calculated value is the sum of the absolute uncertainties

What must be done when multiplying or dividing measurements (in terms of propagation)?

the total percentage uncertainty is the sum of the individual percentage uncertainties. Absolute uncertainties can be calculated from the percentage uncertainty.

How do we calculate uncertainties with exponents?

percentage uncertainty of the raw data is multiplied by the values of the exponent

When does uncertainty not needed to be propagated?

when calculating the mean of a set of data/trials