EXACT Statement

The FREQ Procedure

EXACT Statement

EXACT statistic-options < / computation-option > ;

The EXACT statement requests exact tests or confidence bounds for the specified statistics. The statistic-options specify the statistics for which to provide exact tests or confidence bounds. The computation-option specifies an option for the computation of exact statistics. Computation of exact statistics can require a large amount of time and memory.

Statistic-Options

The statistic-options specify the statistics for which exact tests or confidence bounds are computed. PROC FREQ can compute exact p-values for the following hypothesis tests: chi-square goodness-of-fit test for one-way tables; Pearson chi-square, likelihood-ratio chi-square, Mantel-Haenszel chi-square, Fisher's exact test, Jonckheere-Terpstra test, Cochran-Armitage test for trend, and McNemar's test for two-way tables. PROC FREQ can also compute exact p-values for tests of the following statistics: Pearson correlation coefficient, Spearman correlation coefficient, simple kappa coefficient, and weighted kappa coefficient. PROC FREQ can compute exact p-values for the binomial proportion test, as well as an exact confidence bound for the binomial proportion. Additionally, PROC FREQ can compute exact confidence bounds for odds ratios for 2 ×2 tables.

Table 26.6 lists the available statistic-options and the exact statistics computed. The option names are identical to the corresponding options in the TABLES statement and the OUTPUT statement. You can request exact computations for groups of statistics by using options that are identical to the following TABLES statement options: CHISQ, MEASURES, and AGREE. For example, when you specify the CHISQ option in the EXACT statement, PROC FREQ computes exact p-values for the Pearson chi-square, likelihood-ratio chi-square, and Mantel-Haenszel chi-square tests. You request exact p-values for an individual test by specifying one of the statistic-options shown in Table 26.6.

Table 26.6: EXACT Statement Statistic-Options

Option	Exact Statistics Computed
AGREE	McNemar's test for 2 ×2 tables, simple kappa coefficient, and weighted kappa coefficient
BINOMIAL	binomial proportion test for one-way tables
CHISQ	chi-square goodness-of-fit test for one-way tables; Pearson chi-square, likelihood-ratio chi-square, and Mantel-Haenszel chi-square tests for two-way tables
FISHER	Fisher's exact test
JT	Jonckheere-Terpstra test
KAPPA	test for the simple kappa coefficient
LRCHI	likelihood-ratio chi-square test
MCNEM	McNemar's test
MEASURES	tests for the Pearson correlation and the Spearman correlation, and the odds ratio confidence bounds for 2 ×2 tables
MHCHI	Mantel-Haenszel chi-square test
OR	odds ratio confidence bounds for 2 ×2 tables
PCHI	Pearson chi-square test
PCORR	test for the Pearson correlation coefficient
SCORR	test for the Spearman correlation coefficient
TREND	Cochran-Armitage test for trend
WTKAP	test for the weighted kappa coefficient

Computation-Option

The computation-option specifies an option for computation of exact statistics. You can specify the following computation-option in the EXACT statement.

MAXTIME=value

specifies the maximum time (in seconds) that PROC FREQ can use to compute an exact p-value. If the procedure does not complete the computation within the specified time, it terminates the computation. The value of the MAXTIME= option must be a positive number.

See the "Computational Resources section" for more information.

Using TABLES Statement Options with the EXACT Statement

If you use only one TABLES statement, you do not need to specify options in the TABLES statement that are identical to options appearing in the EXACT statement. PROC FREQ automatically invokes the corresponding TABLES statement option when you specify the option in the EXACT statement. However, when you use multiple TABLES statements and want exact computations, you must specify options in the TABLES statement to compute the desired statistics. PROC FREQ then performs exact computations for all statistics that are also specified in the EXACT statement.

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