Update documentation of the main function

tests/testRandom.c

@@ -65,11 +65,18 @@ double pearsonfunc(double mean1, double mean2, double total12, double var1, doub
  * 1. The mean and variance are correct for random numbers generated by this
  *    ID number.
  * 2. The random numbers from this ID number do not cause correlation in time.
+ *    Correlation is checked using the Pearson correlation coefficient which
+ *    should be sufficiently close to zero.
  * 3. A small offset in ID number of 2, doesn't cause correlation between 
- *    the two sets of random numbers and the mean and variance of this set is 
+ *    the two sets of random numbers (again with the Pearson correlation 
+ *    coefficient) and the mean and variance of this set is 
  *    also correct.
  * 4. Different physical processes in random.h are also uncorrelated and 
- *    produce the correct mean and variance as expected. 
+ *    produce the correct mean and variance as expected. Again the correlation
+ *    is calculated using the Pearson correlation coefficient. 
+ *
+ * More information about the Pearson correlation coefficient can be found in 
+ * the function pearsonfunc above this function.
  *
  * @param none
  */