$6\mathrm{.}24$ Technology for teaching statistics. The Brigham Young University statistics department performed randomized comparative experiments to compare teaching methods. One study compared two levels of technology for large lectures: standard $($overhead projectors and chalk$)$ and multimedia. The "individuals" in the study were the eight lectures in a basic statistics course. There were four instructors, each of whom taught two lectures. Because lecturers differed, a block design was used with the lecturers forming four blocks and each lecturer using the standard technology in one lecture and the multimedia technology in the other. The average of the final exam scores of the students in the lecture was used as the response for each lecture. Suppose the lectures and lecturers were as follows.

$\backslash$table$[[$Lecture$,$Lecturer,Lecture,Lecturer$],[1,$Barney,$5,$Heaton$],[2,$Page,$6,$Page$],[3,$Heaton,$7,$Barney$],[4,$Richardson,$8,$Richardson$]]$

Use a diagram to outline a block design for this experiment. Figure $6\mathrm{.}2$ is a model.