For the hypothetical data contained in Table 13.1, five participants were measured at two occasions. The question of interest is: "is there a difference between Time 1 and Time 2 scores?"
Table 13.1 presents hypothetical data. The null hypothesis to be tested is that population means of Time 1 and Time 2 are equal to one another. This will be tested by forming a difference score. The right-most column of Table 13.1 shows such a difference score, Time 2 score minus Time 1 score, for each subject.