Appendix A1.8, Table A1.3 lists the number of exceedences that can be tolerated for 95 percent confidence that a benchmark is not being exceeded more than 5 percent of the time.
Permitted Exceedances of Maximum Acceptable Values under the Drinking-water Standards for New Zealand 200523
Appendix A1.8, Table A1.3 refers to the number of samples, irrespective of the frequency of sampling. Thus the number of permissible transgressions in 250 samples is the same (7) whether all 250 samples were collected in one day or taken over the course of a year.
Table A1.3: Allowable exceedances (for 95% confidence that the MAV is exceeded for no more than 5% of the time)
| Exceedences | Number of samples |
|---|---|
| 0 | 38–76 |
| 1 | 77–108 |
| 2 | 109–138 |
| 3 | 139–166 |
| 4 | 167–193 |
| 5 | 194–220 |
| 6 | 221–246 |
| 7 | 247–272 |
| 8 | 273–298 |
| 9 | 299–323 |
| 10 | 324–348 |
Table A1.4: Allowable exceedances (for 95% confidence that the MAV is exceeded for no more than 2% of the time)
| Exceedences | Number of samples |
|---|---|
| 0 | 95–193 |
| 1 | 194–274 |
| 2 | 275–349 |
| 3 | 350–420 |
| 4 | 421–489 |
| 5 | 490–556 |
| 6 | 557–621 |
| 7 | 622–686 |
| 8 | 687–750 |
| 9 | 751–813 |
| 10 | 814–875 |
23 The information in Appendix 5 is directly quoted from pages 128–129 of the Drinking-water Standards for New Zealand 2005.
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Appendix 5: Permitted Exceedances of Maximum Acceptable Values under the Drinking-water Standards for New Zealand 2005
May 2009
© Ministry for the Environment