Probability (P) values tell you how likely it is that a value returned by a statistic could have happened by chance in a 2-tailed T-test. The general rule is that the smaller the probability the greater the significance of the statistic. A probability value of less than 0.05 means that there is less than a 5% chance that the result is due to chance. This probability corresponds to the 5% risk and 95% confidence levels. If the statistic has a probability of less than 0.05 then the results are significant at the 95% confidence level.

To see P-values include the option pvals on the tstat statement.

Quantum reports probabilities as a decimal value with three decimal places, where 1.000 corresponds to 100%. A probability of 0.862 indicates that the value of the statistic is 86.2% likely to occur by chance in a 2-tailed T-test. The number of decimal places is not affected by either dec= or decp=.

The way Quantum reports P-values varies according to the type of test you are running; for example, with a test on column proportions Quantum writes the P-values out to a separate file whereas with a significant net difference test the P-values are printed on the table itself.