We can determine the uncertainty in the gradient by drawing lines of maximum and minimum gradients
through their scattered data points. What happens when there is little scatter of the data points? This is
when we draw error bars. Error bars show the range a point is likely to lie in.
The uncertainty in the gradient can be determined as follows:
a. Error bars may be added to each plotted point if the data points are not too scattered.
b. Draw a best fit line through the scattered points (or through the error bars). The worst
acceptable line is then drawn. This will either be the steepest or shallowest line.
c. Determine the gradient of the best fit line and the gradient of the worst acceptable line.
d. Uncertainty = |gradient of best fit line – gradient of worst acceptable line|.
e. The percentage uncertainty in the gradient can be determined as follows:
Percentage Uncertainty = (Uncertainty/Gradient of best fit line) x 100