See statistical significance.

a difference that makes a difference, my former statistical professor often said

a Kaplan-Meier comparison is usually assessed by a log-rank test (which assumes proportional hazards)

a lesser level of difference of charge type from Substantial Difference

Mathematically, it is the difference between tests of two or more variables. The significance difference varies with the desired confidence level.

A decision that an observed difference between two statistics probably did not occur by chance.

In mathematical terms, a difference between tests of two or more variables, which is sufficient to indicate that a similar mailing will produce the same or similar differentiation. The significant difference varies with the confidence level desired. Most direct-mail penetration uses a 95-percent confidence level wherein 95 times out of 100 the results found in the test will come close to the results obtained by duplicating on a retest or combination.