Graphics Reference
In-Depth Information
A conclusion from Fig.
.
is: as factor
comb
goes from
clover
to
clover+
alfalfa
,theresponse
npg
(nitrogen per gram) decreases significantly only for
level
5
of
strain
.
Three-factor Vulcanized Rubber Example
6.6.3
An example of atwo-way interaction plot involving three factorsappears in Fig.
.
.
his is a
factorial experiment designed to compare the wear resistance of
vulcanized rubber. It was desired to maximize wear resistance, along with minimiz-
ing the costs of three factors:
filler
at five quality levels,
pretreatment
(three
methods), and
raw
(four qualities). he data come from Davies (
). As there is
only one observation from each treatment combination, it is assumed that the three-
factor interaction is negligible and therefore available as the model residual.
Figure
.
corresponds to the model with all three main effects and all three two-
factor interactions. he most striking conclusion from Fig.
.
is that for
filler
level
,the change in responsetochanging levels of factor
raw
is different fromwhat
occurs at the other four levels of
filler
.
Figure
.
.
HH Figure
.
, p.
. Main effects and two-way interactions for wear resistance of
vulcanized rubber (File: h
/intx/code/vulcan.intx.s)
