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

in barge construction over the range of ages in our sample the coeffi-
cients of the dummy age variables would show no significant differences
between age groups. A jumbo hopper barge is a fairly simple piece of
equipment. According to naval architects, few design changes in barge
construction have taken place since World War II.
Second, if bargesreceivepreventative maintenance to arrest cor-
rosion and hull damage, rather than being allowed to deteriorate until
maintenance is absolutely necessary, the effects of age on maintenance
cost would disappear. Casual inspection of the firms' records indicates
that this may be the case, many barges receiving, for example, painting
in successive years.
Table 13 presents the results of F-tests performed on each variable
finally included. With the exception of cubic capacity, all variables
are significant at the .999 level of probability. Although the F-value
of the cubic capacity variable was not significant, a one-tailed t-test
performed on the capacity coefficient yields a significant value at the
.90 level of probability. Because of interest in the capacity variable
as a quasi-plant size measure it has been included in.fhe results below.
The Results
The results of the log-linear estimation are presented in Table
12. Looking first at the results for total current output, we see
that the coefficient' of cargo ton-miles is negative and significant.
• The negative sign for cargo ton-miles is an indication that the average
cost of a cargo ton-mile declines throughout the range of current out-
put actually experienced. If one takes the view that each barge is a
"plant" for the production of cargo ton-miles of freight, the average
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