Table 3.

Tiers for the factors of non-genetic sources of information from the field and laboratory phases

Tier 3	Tier 2	Tier 1
Factors randomised in field phase	Factors unrandomised in field phase	Factors unrandomised in laboratory phase
Cultivar	Field block	Day
	Field row	Plate
	Field column	Plate plota
		Plate row
		Plate column

^aPlate plot refers collectively to the four consecutive wells used for a single sample. The aim of this stage in the analysis process is to identify the objects involved in the randomisation and then to determine the factors associated with each set of objects; these groups of factors are referred to as tiers. Here the factors form the non-genetic sources of information from the experimental design elements of the field and laboratory phases. Following Brien [12] the tiers are labelled in reverse chronological order of conduct of the experiment.