Responses among experimental units vary due to many different causes, known and unknown. The process of the separation and comparison of sources of variation is called the Analysis of Variance (AOV). The process is more general than the t-test as any number of treatment means can be simultaneously compared. The sugar beet experiment discussed in Chapter 5 and 6 involved six rates of nitrogen fertilizer. Table 7-1 gives root yield data for the five replications of all six treatments.