`ranuni`or other

`ran___`series of random number generators, you still have the 2

^{32}-1 period generator. SAS's implementation is top of the line of this class of generators, but the class is unsuitable for anything but the simplest of tasks (or teaching demonstrations). Serious modern clinical trial simulation tasks require a period of at least 2

^{64}.

Enter SAS's

`RAND`function.`RAND`takes a string argument that identifies the distribution (e.g. uniform or normal) followed by enough numerical parameters to identify the class member (e.g. normal requires either 0 or 2 numerical parameters&emdash;0 parameter gives you an N(0,1) distribution and 2 parameters identify the mean and variance). The special thing about`RAND`is that it is based on the Mersenne twister algorithm, which has a period of 2^{19937}-1 and very good "randomness" properties.So I hereby recant my criticism of SAS's PRNG capabilities.