Appendix IV to Part 265 - Tests for Significance
40:28.0.1.1.6.27.1.9.19 : Appendix IV
Appendix IV to Part 265 - Tests for Significance
As required in § 265.93(b) the owner or operator must use the
Student's t-test to determine statistically significant changes in
the concentration or value of an indicator parameter in periodic
ground-water samples when compared to the initial background
concentration or value of that indicator parameter. The comparison
must consider individually each of the wells in the monitoring
system. For three of the indicator parameters (specific
conductance, total organic carbon, and total organic halogen) a
single-tailed Student's t-test must be used to test at the 0.01
level of significance for significant increases over background.
The difference test for pH must be a two-tailed Student's t-test at
the overall 0.01 level of significance.
The student's t-test involves calculation of the value of a
t-statistic for each comparison of the mean (average) concentration
or value (based on a minimum of four replicate measurements) of an
indicator parameter with its initial background concentration or
value. The calculated value of the t-statistic must then be
compared to the value of the t-statistic found in a table for
t-test of significance at the specified level of significance. A
calculated value of t which exceeds the value of t found in the
table indicates a statistically significant change in the
concentration or value of the indicator parameter.
Formulae for calculation of the t-statistic and tables for
t-test of significance can be found in most introductory statistics
texts.