INDEPENDENT Subcommand (NPTESTS command)

The INDEPENDENT subcommand produces independent samples nonparametric tests. The TEST and GROUP keywords are required, all other keywords are optional. If INDEPENDENT is specified with none of the optional keywords, the following tests are performed automatically:

If the grouping field has only two values, continuous fields are tested using a Mann-Whitney test.
If the grouping field has more than two values, continuous fields are tested using a Kruskal-Wallis test.
If there are no continuous fields on the TEST keyword, no tests are performed.

TEST Keyword

The TEST keyword lists the fields that you want to test.

Specify one or more continuous fields. Independent samples tests are only applicable to continuous fields.

GROUP Keyword

The GROUP keyword specifies the field used to determine groups. The test is performed using the values found in the sample to define the groups. Note that certain tests are not applicable when there are more than two groups. NPTESTS automatically determines which tests are applicable. See the individual keyword descriptions for details.

Specify a categorical field. A grouping field that does not have nominal or ordinal measurement level will cause an error.
GROUP applies to all fields that are specified on the TEST keyword.

MANN_WHITNEY Keyword

The MANN_WHITNEY keyword produces an independent samples test of whether two samples are from the same population. The test statistic uses the rank of each case to test whether the groups are drawn from the same population.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The first value in ascending order of the grouping field defines the first group and the second value defines the second. If the grouping field has more than two values, the test is not performed.

WALD_WOLFOWITZ Keyword

The WALD_WOLFOWITZ keyword produces an independent samples test whether the distribution of a field is the same in two independent samples. A runs test is performed with group membership as the criterion.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The first value in ascending order of the grouping field defines the first group and the second value defines the second. If the grouping field has more than two values, the test is not performed.

KOLMOGOROV_SMIRNOV Keyword

The KOLMOGOROV_SMIRNOV keyword produces an independent samples test of whether the distribution of a field is the same in two independent samples that are defined by a grouping field. The test is sensitive to any difference in median, dispersion, skewness, and so forth, between the two distributions.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The first value in ascending order of the grouping field defines the first group and the second value defines the second. If the grouping field has more than two values, the test is not performed.

MOSES Keyword

     [MOSES([TRIMOUTLIERS={SAMPLE**}])]
                          {integer }

The MOSES keyword produces an independent samples test of whether the range of a continuous or ordinal field is the same in a control group and a comparison group.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The test specifications given on the MOSES keyword apply to all Moses tests performed.
The first value in ascending order of the grouping field defines the control group and the second defines the comparison group. If the grouping field has more than two values, the test is not performed.

TRIMOUTLIERS= SAMPLE|integer. Records to trim from each end of the range of the control group to remove outliers. SAMPLE trims 5% of the records from each end of the range of the control group to remove outliers, with a minimum of 1 record removed from each end. Specifying an integer causes that exact number of records to be trimmed. SAMPLE is the default.

HODGES_LEHMAN Keyword

The HODGES_LEHMAN keyword produces an independent samples estimate and confidence interval for the difference in the medians of two groups.

A separate confidence interval is computed for each and every continuous and ordinal field specified on the TEST keyword.
The first value in ascending order of the grouping field defines the first group and the second value defines the second. If the grouping field has more than two values, the confidence interval is not produced.

KRUSKAL_WALLIS Keyword

     [KRUSKAL_WALLIS([COMPARE={PAIRWISE**}])]
                              {STEPWISE  }
                              {NONE      }

The KRUSKAL_WALLIS keyword produces an independent samples test of whether k independent samples that are defined by a grouping field are from the same population.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The test specifications given on the KRUSKAL_WALLIS keyword apply to all tests performed.

COMPARE= PAIRWISE | STEPWISE | NONE. Multiple comparisons. The COMPARE keyword controls how and whether multiple comparisons should be performed. PAIRWISE produces all pairwise multiple comparisons. STEPWISE produces stepwise stepdown comparisons. NONE turns off multiple comparisons. By default, all pairwise comparisons are produced.

MEDIAN Keyword

     [MEDIAN([TESTVALUE={SAMPLE**}]  [COMPARE={PAIRWISE**}])]
                        {value   }            {STEPWISE  }
                                              {NONE      }

The MEDIAN keyword produces an independent samples test of whether k independent samples are drawn from populations with the same median.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The test specifications given on the MEDIAN keyword apply to all tests performed.

TESTVALUE= SAMPLE|value. Median value to use in the test. SAMPLE causes the test to be performed using the sample median, calculated from all records that are included in the test. Alternatively, you can specify an exact value. SAMPLE is the default.

COMPARE= PAIRWISE| STEPWISE| NONE. Multiple comparisons. The COMPARE keyword controls how and whether multiple comparisons should be performed. PAIRWISE produces all pairwise multiple comparisons. STEPWISE produces stepwise stepdown comparisons. NONE turns off multiple comparisons. By default, all pairwise comparisons are produced.

JONCKHEERE_TERPSTRA Keyword

     [JONCKHEERE_TERPSTRA(
         [ORDER={ASCENDING**      }]  [COMPARE={PAIRWISE**}]
                {DESCENDING       }            {STEPWISE  }
                                               {NONE      }
      )]

The JONCKHEERE-TERPSTRA keyword produces an independent samples test of whether k independent samples that are defined by a grouping field are from the same population. This test is particularly powerful when the k populations have a natural ordering.

A separate test is performed for each and every continuous and ordinal field specified on the TEST keyword.
The test specifications given on the JONCKHEERE_TERPSTRA keyword apply to all tests performed.

ORDER=ASCENDING| DESCENDING. Order of the k populations. ASCENDING specifies the alternative hypothesis that the location parameter of the first group is less than or equal to the second, which is less than or equal to the third, and so on. This is the default. DESCENDING specifies the alternative hypothesis that the location parameter of the first group is greater than or equal to the second, which is greater than or equal to the third, and so on. For both options, the alternative hypothesis also assumes that the locations are not all equal.

COMPARE=PAIRWISE|STEPWISE|NONE. Multiple comparisons. The COMPARE keyword controls how and whether multiple comparisons should be performed. PAIRWISE produces all pairwise multiple comparisons. STEPWISE produces stepwise stepdown comparisons. NONE turns off multiple comparisons. By default, all pairwise comparisons are produced.