Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

significantly different from the 'normal' discriminators when the differences
between the two discriminators are compared to the standard deviations of
the sub-samples. This comparison is made in Table X.
Variates R.. -
13 13
X 31
X 21
X 32
X 31
X 21
X 32
Table X (1)
50
Actual Probabilities of Correct
Classification
_
1.440 .82 .85 -
.045 .76 - .77
.095 . .56 .81
Standard Deviation
5.39 2.89 -
3.36 - 3.02
. 2.68 2.06
Moreover, the actual probabilities of correct classification are of a
similar order.
Considering the deficienaes of the distribution-free method,
the nature of our information, and the apparent robustness of the 'normal'
method, we think that the latter should be adopted.
Let us note that to improve the accuracy of the results, it was
decided not to use the assumption that the variances were equal, even in the
cases where an F-test sustained such a hypothesis. AlthOugh very convenient
in computing the's this hypothesis would decrease the robustness of the
procedure. It is also unwarranted by the nature of the samples.
(1) -
Xij is taken as the mid-value of the intervals given in Table IX.