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K-S test of normality in NPAR TESTS and NPTESTS does not use Lilliefors correction prior to SPSS Statistics 21.0.0.1

Troubleshooting


Problem

I wish to test the fit of a variable to a normal distribution, using the 1-sample Kolmogorov-Smirnov (K-S) test in SPSS Statistics 21.0 or a prior version. There are three SPSS procedures that compute a K-S test for normality and they report two very different p (significance) values for the same data. If I choose 'Analyze->Descriptive Statistics->Explore' from the menus, click the Plots button and check "Normality plots with tests", then the EXAMINE command is run and the K-S test with Lilliefors correction (for sample-based parameters) is printed. If I choose 'Analyze->Nonparametric Tests->Legacy Dialogs->1-Sample K-S' and take the default test for a normal distribution, then the NPAR TESTS command is run and the K-S test results are also reported. (In versions prior to Statistics 18., the path to K-S in NPAR TESTS was Analyze->Nonparametric Tests->1-Sample K-S.) If I choose 'Analyze->Nonparametric Tests->One Sample' and check the Kolmogorov-Smirnov test in the 'Settings-Choose Tests' dialog, with the 'Use sample data' default for parameters, then the NPTESTS command is run and the K-S results are presented in the model viewer. However, the significance levels reported in the Explore K-S results are typically smaller than the significance levels reported in the NPAR TESTS or NPTESTS (with sample parameters) results. I suspect that the discrepancy is due to the fact that the K-S test in EXAMINE incorporates the Lilliefors correction to reduce the likelihood of a Type II error when sample estimates of the parameters are used. Why is the Lilliefors correction not implemented in the K-S test in the Nonparametric Tests procedures (the NPAR TESTS and NPTESTS commands)?

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Historical Number

24957

Document Information

Modified date:
16 June 2026

UID

swg21477354