The FREQTAB Procedure

specifies the level of the confidence limits for Monte Carlo p-value estimates. The value of must be between 0 and 1; a confidence level of produces % confidence limits. By default ALPHA=0.01, which 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 FREQTAB can use to compute an exact p-value. If the procedure does not complete the computation within the specified time, the computation terminates. The MAXTIME= value must be a positive number. This option is available for Monte Carlo estimation of exact p-values, in addition to direct exact p-value computation. For more information, see the section Computational Resources.

requests Monte Carlo estimation of exact p-values instead of direct exact p-value computation. Monte Carlo estimation can be useful for large problems that require a considerable amount of time and memory for exact computations but for which asymptotic approximations might not be sufficient. For more information, see the section Monte Carlo Estimation.

This option is available for all EXACT statistic-options except the BINOMIAL option and the following options that apply only to or tables: BARNARD, COMOR, EQOR, MCNEM, OR, RELRISK, and RISKDIFF. PROC FREQTAB always computes exact tests or confidence limits (not Monte Carlo estimates) for these statistics.

The ALPHA=, N=, and SEED= options invoke the MC option.

requests exact mid p-values for the exact tests. The exact mid p-value is defined as the exact p-value minus half the exact point probability. For more information, see the section Definition of p-Values.

The MIDP option is available for all EXACT statement statistic-options except the following: BARNARD, EQOR, OR, RELRISK, and RISKDIFF. You cannot specify both the MIDP option and the MC option.

specifies the number of samples for Monte Carlo estimation. The value of n must be a positive integer, and the default is 10,000. Larger values of n produce more precise estimates of exact p-values. Because larger values of n generate more samples, the computation time increases.

The N= option invokes the MC option.

specifies the display format for exact p-values. PROC FREQTAB applies this format to one- and two-sided exact p-values, exact point probabilities, and exact mid p-values. By default, PROC FREQTAB displays exact p-values in the PVALUE6.4 format.

You can provide a format-name or you can specify PFORMAT=EXACT to control the format of exact p-values. The value of format-name can be any standard SAS numeric format or a user-defined format. The format length must not exceed 24. For information about formats, see the FORMAT procedure in the Base SAS Procedures Guide and the FORMAT statement and SAS format in SAS Formats and Informats: Reference.

If you specify PFORMAT=EXACT, PROC FREQTAB uses the 6.4 format to display exact p-values that are greater than or equal to 0.001; the procedure uses the E10.3 format to display values that are between 0.000 and 0.001. This is the format that PROC FREQTAB uses to display exact p-values in releases before SAS/STAT 12.3. Beginning in SAS/STAT 12.3, by default PROC FREQTAB uses the PVALUE6.4 format to display exact p-values.

requests exact point probabilities for the exact tests. The exact point probability is the exact probability that the test statistic equals the observed value. For more information, see the section Definition of p-Values.

The POINT option is available for all EXACT statement statistic-options except the following: BARNARD, EQOR, OR, RELRISK, and RISKDIFF. You cannot specify both the POINT option and 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 0, PROC FREQTAB uses the time of day from the computer’s clock to obtain the initial seed.

The SEED= option invokes the MC option.