See Completely Randomised Design . See Randomised Complete Block Design . See Factorial Design . In experiments, a treatment is something that researchers administer to experimantal units . Level' is also used for categorical variables, such as Drugs A, B, and C, where the three are different kinds of drug, not different amounts of the same thing.
Different treatments constitute different levels of a factor.
For example, three different groups of runners are subjected to different training methods. The runners are the experimental units, the training methods, the treatments, where the three types of training methods constitute three levels of the factor 'type of training'. The one way analysis of variance allows us to compare several groups of observations, all of which are independent but possibly with a different mean for each group. A test of great importance is whether or not all the means are equal. We are classifying 'one-way' according to the group or treatment.