In a study of the use of macroinvertebrate communities as pollution indicators, the effectiveness of a numerical species diversity index to indicate aquatic degradation due to acid mine drainage was investigated. A high diversity index should indicate an unstressed aquatic system. Two sampling stations were chose, one upstream and one downstream of the discharge point. Twelve samples were taken at each over the course of a month and gave the summarized results shown below. Earlier work suggested that an assumption of Normality is reasonable.
Downstream: Mean 2.01, SD 0.508
Upstream: Mean 3.41, SD 0.872
Formally test the equality of the long-run standard deviations of the up and downstream samples.