Data management

It was decided to commence each 'year' in March for the purposes of this analysis since this was when the rains generally commenced. The months from November to February were generally dry. Thus, for example, year 1990 in this case study refers to the period from March 1990 to February 1991 - with means calculated from March to August and September to February, respectively.

The data management process was divided into two steps:

• determine for each variable which 6-monthly periods could be used during the study to calculate mean values. (As will be seen on the next page, mean values could not be calculated for all periods for some variables.)

• describe for each variable the steps to be taken to reduce the data to 6-month animal values