When leather is used to produce furniture or clothes, its shrinkage is an important consideration. An experiment was conducted to discover the differences between four different preparation methods in terms of the resulting shrinkages of the leather. Seven batches of leather were split into four parts each, which were then randomly assigned to each of the four preparation methods. The shrinkage measurements are given in DS 11.4.8. What conclusions can you draw from this data set about the differences between the four different preparation methods?