Calculate uncertainty in a graph gradient
Gradient
Enter both lines
Your result
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The uncertainty in a graph gradient is the difference between the best and worst gradients, and dividing it by the best gradient and multiplying by 100 gives it as a percentage.
Questions people ask
How do you find the uncertainty in a gradient?
Draw the best line, then the steepest or shallowest line that still goes through all the error bars. The uncertainty is the difference between their gradients.
How do you find the percentage uncertainty in a gradient?
Divide the difference between the best and worst gradients by the best gradient and multiply by 100.
Should the points be data points?
No. Read the two points off each drawn line, far apart, rather than using your plotted data.
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How we work this out
What it does
Enter two points on your best line and two on your worst: get the gradient with its uncertainty.
AQA A-level Physics (7408): the uncertainty in a gradient from a best line and a worst acceptable line drawn through the error bars.
Method
- Gradient of each line = (y₂ − y₁) ÷ (x₂ − x₁), after any axis multiplier.
- Absolute uncertainty = the difference between the best and worst gradients.
- Percentage uncertainty = absolute uncertainty ÷ best gradient × 100.
- The uncertainty is quoted to 1 significant figure and the gradient to the same decimal place.