Plotting the Bland-Altman limits of agreement

Plot a difference plot and limits of agreement.

  1. Select a cell in the dataset.
  2. On the Analyse-it ribbon tab, in the Statistical Analyses group, click Method Comparison, and then click Bland-Altman.
    The analysis task pane opens.
  3. If the data are in 2 variables:
    1. In the X drop-down list, select the comparative or reference measurement procedure variable.
    2. In the Y drop-down list, select the test measurement procedure variable.
    Note: If the variables consist of replicate measurements, select the variable name that spans all the replicate columns.
  4. If the data are in 2 variables with a separate variable identifying replicates of each item:
    1. In the X drop-down list, select the comparative or reference measurement procedure variable.
    2. In the Y drop-down list, select the test measurement procedure variable.
    3. In the Item drop-down list, select the variable identifying each item.
  5. If the data are in a single variable with a separate variable matching each item and a variable identifying the method:
    1. In the Model drop-down menu, select Matched Pairs.
    2. In the Y drop-down list, select the measurement variable.
    3. In the Item drop-down list, select the item variable that identifies each item.
    4. In the Method drop-down list, select the method variable.
  6. In the D drop-down list, select:
    Option Description
    Difference Plot the differences on the vertical axis.
    Relative Difference Plot the differences relative to Z on the vertical axis.
    Ratio Plot the ratio of the values on the vertical axis.
  7. In the on Z drop-down list, select:
    Option Description
    X Plot X as a reference method on the horizontal axis.
    (X+Y)/2 Plot the average on the horizontal axis. Neither X or Y are reference methods.
  8. In the Mean function drop-down list, select:
    Option Description
    Constant There is a constant relationship between D and Z.
    Linear function There is a linear relationship between D and Z.
  9. In the SD drop-down list, select:
    Option Description
    Constant The measurement error is constant throughout the measuring interval.
    Linear function The measurement error is linear across the measuring interval.
  10. Click Calculate.