The NPAR1WAY Procedure 
EXACT Statement 
Note:PROC NPAR1WAY computes exact tests with fast and efficient algorithms that are superior to direct enumeration. Exact tests are appropriate when a data set is small, sparse, skewed, or heavily tied. For some large problems, computation of exact tests might require a large amount of time and memory. Consider using asymptotic tests for such problems. Alternatively, when asymptotic methods might not be sufficient for such large problems, consider using Monte Carlo estimation of exact pvalues. See the section Computational Resources for more information.
The statisticoptions specify the statistics for exact tests.
Exact pvalues are available for all nonparametric tests of location and scale differences that are produced by PROC NPAR1WAY. These include tests based on the following scores: Wilcoxon, median, Van der Waerden (normal), Savage, SiegelTukey, AnsariBradley, Klotz, Mood, and Conover. Additionally, exact pvalues are available for tests that use the raw input data as scores. The procedure computes exact pvalues when the data are classified into two levels (twosample tests) and when the data are classified into more than two levels (multisample tests). Twosample tests are based on simple linear rank statistics. Multisample tests are based on oneway ANOVA statistics. See the section Exact Tests for details.
Exact pvalues are also available for the twosample KolmogorovSmirnov test. Additionally, exact confidence limits are available for the HodgesLehmann estimate of location shift. See the section HodgesLehmann Estimation of Location Shift for details.
Table 62.3 lists the available statisticoptions and the exact tests computed. The option names are identical to the corresponding options in the PROC NPAR1WAY statement and the OUTPUT statement.
If you list no statisticoptions in the EXACT statement, then PROC NPAR1WAY computes all available exact pvalues for those tests that you request in the PROC NPAR1WAY statement.
StatisticOption 
Exact Test Computed 

AnsariBradley test 

Conover test 

HodgesLehmann confidence limits 

Klotz test 

Twosample KolmogorovSmirnov test 

Median test 

Mood test 

Savage test 

Test with input data as scores 

SiegelTukey test 

Van der Waerden (normal scores) test 

Wilcoxon test for twosample data or 

KruskalWallis test for multisample data 
The computationoptions specify options for computation of exact statistics. You can specify the following computationoptions in the EXACT statement:
specifies the level of the confidence limits for Monte Carlo pvalue estimates. The value of must be between 0 and 1, and the default is 0.01. A confidence level of produces % confidence limits. The default of ALPHA=0.01 produces 99% confidence limits for the Monte Carlo estimates.
The ALPHA= option invokes the MC option.
specifies the maximum clock time (in seconds) that PROC NPAR1WAY can use to compute an exact pvalue. If the procedure does not complete the computation within the specified time, the computation terminates. The value of MAXTIME= must be a positive number. The MAXTIME= option is valid for both Monte Carlo estimation of exact pvalues and direct exact pvalue computation. See the section Computational Resources for more information.
requests Monte Carlo estimation of exact pvalues, instead of direct exact pvalue computation. Monte Carlo estimation can be useful for large problems that require a great amount of time and memory for exact computations but for which asymptotic approximations might not be sufficient. See the section Monte Carlo Estimation for more information.
The MC option is available for all EXACT statement statisticoptions except the HL option, which produces exact HodgesLehmann confidence limits. The ALPHA=, N=, and SEED= options also invoke the MC option.
specifies the number of samples for Monte Carlo estimation. The value of must be a positive integer, and the default is 10,000 samples. Larger values of n produce more precise estimates of exact pvalues. Because larger values of n generate more samples, the computation time increases.
The N= option invokes the MC option.
requests exact point probabilities for the test statistics.
The POINT option is available for all the EXACT statement statisticoptions except the HL option, which produces exact HodgesLehmann confidence limits. The POINT option is not available with the MC option.
specifies the initial seed for random number generation for Monte Carlo estimation. The value of the SEED= option must be an integer. If you do not specify the SEED= option or if the SEED= value is negative or zero, PROC NPAR1WAY uses the time of day from the computer’s clock to obtain the initial seed.
The SEED= option invokes the MC option.
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