What Is a “Significant” Adverse Cumulative Effect?
The key to the definition now lies in the word “significant,” and “significant” is one of those words that has a different definition for every person who uses it. Two general categories of definition are particularly meaningful in this context, however. To a scientist, a “significant” change is one that can be demonstrated with a specified level of certainty. For example, if data show that there is only a probability of 0.13 that a measured 1 percent increase in sediment load would appear by chance, then that change is statistically significant at the 87 percent confidence level, irrespective of whether a 1 percent change makes a difference to anything that anyone cares about. The second category of definition concentrates on the nature of the interaction: if someone cares about a change or if the change affects their activities or options, it is “significant” or “meaningful” to them. This definition does not require that the change be definable statistically. An unprecedented activit
