66
independent variables and interaction terms were tested. The selection
of the final equation for each crop was based upon the extent to which
it was believed to describe observed conditions in the area, and upon
statistical indicators of significance. The statistical criteria in-
2
eluded the students "t" values for individual variables, and R values
for the function as a whole.
Generally the level of significance of the regression coefficients
was a =.05 or lower. However, several variables were included in the
final production functions for which the coefficients were significant
at the a =.20 or a =.25 levels. These latter levels were considered
acceptable given the nature of the data used. The data were obtained
by interviews and were based on recall, not written records. The sizes
of the samples were small and this may have contributed to the lower
confidence levels for a number of coefficients. Also, it is believed
that these results would provide useful guidance in any future investi
gation and experimentation.
Cotton
The following production function was derived for cotton:
Y = -3266.82 + 253.10 Hp 25.00 Mp2 + 23.92 L .038 L2 + 1.812 (NCI)
-.0011 (NCI)2 + .00000022 (NCI)3
where:
Y = yield of seedcotton in kilograms per hectare
Mp = tractor hours per hectare in soil preparation (pre-planting)
L = hours of labor per hectare
NCI = value of fertilizer and insecticide per hectare, in pesos.
In Table 9 the values derived from this equation and the mean value of
each input based upon sample data are summarized.