Ecology of the burrowing amphipod, Pontoporeia affinis, in Lake Michigan / by Wayne Paul Alley.

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the wide range of variability that exists in the average number of
Pontoporeia found in the sediments containing little organic carbon.
Distance from Shore: Samples of Pontoporeia were combined into
groups that were the same distance from shore (Fig. 41). Stations two
miles from shore represented the most inshore sampling area while a
station 38 miles from shore was the greatest sampling distance. There
appears to be a general inverse relationship between amphipod abundance
and distance from shore. The greatest variability in amphipod abundance
occurred at the more inshore stations (Fig. 42).
Stepwise Multiple Regression Analysis of Environmental Parameters
The lake was first treated as a single system in the examination
of the interrelationships of Pontoporeia and its environment. It was
next divided into four depth zones: 10-35 m, 36-65 m, 66-105 m and
greater than 105 m. Stations in the 10-35 m zone were considered the
sublittoral and those deeper than 35 m, profundal.
First the simple correlation coefficients were calculated for the
four depth zones and all depths combined, then the stepwise multiple
regression equation was computed for these data. A 5 percent level of
significance was chosen for the F test that controls the likelihood of
committing the error of entering a variable into the prediction equation
when it is insignificant. This same level of significance was also used
for the F test that controls the error of removing a variable from the
equation when it is significant. A multiple correlation coefficient and a