Traditional
 Maize

 60 Maize in twin rows
 with potatoes



 Confidence
 Coefficient


 80



 90



 100
 0 0.5 1.0 1.5 2.0

 Net Income/Cost
FIG.VII-9. Distribution of confidence intervals for
 return to cost, traditional maize versus
 twin rows with potatoes.

 If one examines the system involved, it is evident
that it is not a substitute for maize, as was implied in
the calculation of the acceptability index, but rather a
means of allowing farmers to produce an alternative cash
crop (potatoes) without reducing the amount of maize
produced on the farm. Therefore, a more relevant measure
of acceptability would be to estimate the index based on
potato production on each farm, rather than on maize
production. Data are not available from the directed
survey on this criterion. However, it would be
anticipated that the farmers who used the system the year
following the trial planted a high proportion of their
potatoes in the new system. For example, if the only
potatoes the four farmers planted were in the new system,
the index of acceptability would be 57.