2.2- measurements

How does systematic error arise?

The use of faulty instruments or flaws in experimental method

Precision

How close values are to each other

Accuracy

How close measurement is to true value

Uncertainty

A range of values around a measurement within which the true value is expected to lie and is a true estimate

Absaloute uncertainty

Where uncertainty is given as a fixed quantity

Its expressed in the same units as the measurement

Fractional/ percentage uncertainty

Where uncertainty is given as a percentage or fraction of the measurement

Percentage uncertainty formula

Uncertainty in a reading

+- half of smallest division

Uncertainty in a measurement

+- smallest division

Uncertainty in repeated data

+- range

Range formula

Max - minimum

Uncertainties in digital readings

+- last significant digit

Eg 12.4V → +- 0.1V

Uncertainties in natural log

Uncertainty in x/ over x

How can uncertainty be shown in a graph

As an error bar

How do you combine percentage uncertainties

Multiply percentage uncertainty by the power

Worst line of best fit

Steepest or shallowest possible line which fits within all the error bars

Formula for percentage uncertainty in the gradient

Percentage uncertainty in the y intercept formula