The three principles of experimental design are replication, randomization, and local control. Replication is important because it is the repipation of the experiment on many different units or subjects, this gets the experiment more precise, increases the accuracy and improves the co-effiectn of variation. Next for randomization, that is important because providing a random sample eliminates bias results most of the time, it also helps protect the experiment against the effects of the factors that can't be controlled perfectly. Lastly the local control is important because it includes all practices or techniques used to minimize the experimental error which includes balancing, blocking, and grouping of experimental units.