Case study 6: Field studies to evaluate the benefits on milk production of providing smallholder farmers in Kenya access to credit to allow shifting of concentrate feeding to early lactation

Data management

Next, we need to group the data into five lactation phases, four of 7 week intervals and a remainder, so that we can later analyse the association between milk yield and concentrate fed at different phases of lactation. We do this using Data Form Groups (Factors)... and enter the values 49, 98, 147, 196 to define group endings (see dialog box below) This results in values of 24, 73, 120, 169, 225 representing the medians for the five groups. We can convert these into values 1, 2, 3, 4, 5 via Spread → Factor → Change levels…

We save this file as a GenStat worksheet in CS6Data2. This file provides the basis for fitting Wood's model in Statistical modelling to calculate the average relationship between milk yield and day of lactation.