About reference lines

Reference lines are horizontal or vertical lines that span the data region of a graph to designate goals or demarcations.

For example, the reference line on this bar chart of monthly sales represents sales quotas.

Add reference lines to a graph

You can add reference lines to most Minitab graphs.

Note

You must use the scale units on the graph to position the reference lines. For example, if the y-scale has been transformed so that the tick marks are displayed in transformed units, you must enter the reference line position in the transformed units.

  • To add references lines when you create a graph: in the dialog box for the graph you are creating, click Scale, click the Reference Lines tab, and then specify the reference line positions.
  • To add reference lines to an existing graph: right-click the graph, choose Add > Reference Lines, and then specify the reference line positions.

Example of placing a reference line in front of bars, symbols, or other data displays

Reference lines are displayed behind data displays and may be difficult to see with some graphs, such as histograms. To create a reference line that sits in front of the graph's data display, use a calculated line instead. Enter coordinates in your worksheet representing the two end points of the reference line, then use Editor > Add > Calculated Line to draw the line.

Histogram with a line in front of the bars

For example, suppose you have created a histogram and you want to add a reference line at y = 8.

  1. Open the Minitab sample data set PulseRates.MTW.
  2. Choose Graph > Histogram > Simple and click OK.
  3. In Graph variables, enter Pulse1. Click OK.
  4. Find the maximum and minimum of the x-axis.
    1. Double-click the x-axis.
    2. On the Scale tab, under Scale Range, note the values. Click OK.
  5. In C10, enter 8 in row 1 and 8 in row 2.
  6. In C11, enter 50.83 (the minimum) in row 1 and 104.17 (the maximum) in row 2.
  7. Click the graph window to activate it. Choose Editor > Add > Calculated Line.
  8. In Y column, enter C10.
  9. In X column, enter C11. Click OK.
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