Even though the study is not a controlled experiment, the point made about blocking is still valid, and in this lab we will use the same terminology used in discussing controlled experiments.

In Chapter 3 of the Petruccelli, Nandram and Chen book, the basic motivations for blocking in experimental design are discussed.

In particular, the completely randomized design is contrasted with the randomized complete block design.

Pairing is the simplest form of blocking. In fact, it is the special case of the randomized complete block design in which there are two treatments.

The design of this study will be what is called a paired comparison design.

A paired comparison design is the simplest version of a randomized complete block design.

To demonstrate the effect of blocking (or, in this case, pairing), the data will be analyzed in two different ways: first, as paired comparisons (paired by student), and then as if the data resulted from a completely randomized design (which does not use student pairing).

The results should show you that "block what you can, randomize the rest," is good advice.