An experimenter is planning an agricultural field experiment to compare the yields of 25 varieties of corn. She will use a randomized blocks design with six blocks; thus, there will be 150 plots, and the yield of each plot must be measured. The experimenter realizes that the time required to harvest and weigh all the plots is so long that rain might interrupt the operation. If rain should intervene, there could be a yield difference between the harvests before and after the rain. The experimenter is considering the following plans.
Plan I. Harvest all plots of variety 1 first, all of variety 2 next, and so on.
Plan II. Harvest all plots of block 1 first, all of block 2 next, and so on.
Which plan is better? Why?