Factorials.

Abstract

Abstract This chapter focuses on factorials. Experiments involving two or more factors, each at two or more levels, are called 'factorial experiments'. There is no such thing as a factorial design. Factorial refers to treatment structure. Factorial treatment structures are combined in an efficient experimental design. When considering two or more factors, it introduces the concepts of 'main effects' and 'interactive effects' (interactions). The 'main effect' of a factor is a measure of the change in the response variable to changes in the level of the factor, averaged over all levels of all other factors in an experiment. An 'interaction' occurs when the response to various levels of one factor changes as the levels of another factor change. A single-factor experiment, with the factor 'nitrogen application rate' at four levels to evaluate strawberry yield, and modify it to now include the concept of a factorial treatment structure in a completely random design were conducted. The significance levels for time (0.0926) and rate (0.4287) were neither significant. Thus it doesn't seem to matter when nitrogen is applied or not; there is no effect of nitrogen application on strawberry yield.