Data management

It has been shown previously (Leak et al., 1996) that tsetse control often takes a little while to achieve impact. Notice that the changes in tsetse apparent density, body weight and PCV tended to take effect the year after tsetse control was implemented. A similar tendency was also apparent for many of the other variables.

We thus define a second column (headed lagged) in which the (0, 1) codes have been moved down one line. Since the study involved separate methods of tsetse control and different periods without control we have also define a third column (headed Period) with codes 1 and 2. (see CS10Data5). We shall use these two variables (lagged and period) in our statistical modelling.