Test for Equal Shapes or Scales
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When your failure/repair data are from more than one system, Minitab provides:

·    A test for equal shapes - if you do not provide a known shape

·    A for equality of the scale parameter - if you provide a known shape

·    A test for equal MTBFs - if the shape is set at 1

Each of these tests uses the Bartlett's modified likelihood ratio test whenever possible.

The hypotheses for these tests are:

·    H0: all of the shapes (or scales or MTBFs) are equal

·    H1: at least one of the shapes (or scales or MTBFs) is different

When estimating a parametric growth curve, Minitab assumes that all systems within a single data column are from identical processes. If you reject the null hypothesis and conclude that the shapes (or scales or MTBFs) are unequal, you cannot make this assumption. In this case, you should analyze the data from different systems separately.

Note    These tests are not available for interval data.