2001-12-11_PERMIT FILE - C1981019 ‎(4)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 07 Item 06 Hydrologic & Erosional Characteristics of Regraded Surface Coal Mined Land
• Media Type: D
• Archive: No

59
relationship between a dependent variable and a set of independent var-
iables. During the first step the independent variable most highly
correlated with the dependent variable is selected for the equation. The
next step selects from among the remaining independent variables the
one which, when paired with the independent variable already selected,
is most highly correlated with the dependent variable. The process con-
h
i
i
i
i
i
l
l t
e var
a-
t
nues adding independent var
ables to the equat
on unt
l a
tiles are entered into the equation or until the variable being added is
not statistically significant. Occasionally a variable already in the
equation may become superfluous because of its relationship with sub-
sequent variables added. At each step all variables are re-examined
i
d f
ifi
d
i
rom
gn
roppe
cant are
cally s
and any which are no longer statist
the equation (Kleinbaum and Kupper, 1978). Independent variables tested
• in this study are summarized in Table 11. A matrix of correlation
coefficients showing the simple correlation between the independent
variables is given in Table 12.
l infiltration
i
n
f fi
A
l
f
h
e regress
o
na
o
summary of the resu
ts o
t
capacity on all of the independent variables is given in Table 13.
WETTING was the first variable added to the regression equation because,
following the above discussion, the absolute value of the coefficient of
correlation (r = .449, "simple r" - Table 13) with final infiltration
capacity is largest. MULCH, the second variable added to the regression
equation, appears to be an important determinant of final infiltration
capacity; however, the somewhat arbitrary manner in which values were
assigned to the qualitative measurements of the degree of effective
• mulch cover may make any conclusions about MULCH dubious.