Meniscus midges of the genus Dixa are found in running water and are indicators of surface
pollutants. A biologist collected random samples of pupae from three streams in different states
of eutrophication: oligotrophic, mesotrophic and eutrophic. The table below shows the
frequencies of four species of midges found in the three rivers.
Oligotrophic Mesotrophic Eutrophic
Species A 12 14 35
Species B 7 6 12
Species C 5 22 7
Species D 17 9 11
Using a 1% significance level, formally test for association between the degree of eutrophication
and species of midges. If you find an association, describe it.
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