Question

How can one get the error bars for a plot? Are there error bars for both the horizontal and vertical
axes, or just the vertical axes? Explain.

A student is trying to calculate the volume of a metal sphere. She measures the diameter to be 3.56
cm. The uncertainty in the ruler is 1 mm. What is the absolute uncertainty in the volume
measurement?

Answer 1

Error bars are used to indicate the estimated error in a measurement. In other words, an error bar indicates the uncertainty in a value. Bar charts and line charts can display vertical errors. Scatter plots can display both vertical and horizontal errors. The image below shows all four possible error bars on a scatter plot marker. This means that if you use reversed scales in a visualization, or change orientation of the bars in a bar chart, the error bars will also be reversed or change orientation respectively. For example, for a scatter plot with a reversed Y-axis, an upper vertical error will be displayed below the marker instead of above the marker. For a bar chart with horizontal bars and non-reversed scale, an upper horizontal error will be displayed to the right of the bar.