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In your MYP or IG course you should have been told to use a sharp pencil to draw a small cross to represent a data point on a graph, or a dot with a ring round it. The diameter of the ring should represent the error in the reading.
In IB, we do things more precisely.
Error bars show the actual uncertainty above and below the data point. They can be errors in either the dependent x or the independent y variable or both. In the following example we’ll only concern ourselves with an uncertainty in y.
Suppose we want to try to plot a graph of the speed of a car, starting from rest for the first few seconds. If we try to read off the numbers on the speedometer and write them down, there’ll be a lot of uncertainty in the result. Nevertheless, let’s try just to see…
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