The idea in this assignment is to sort your 12 scores into four groups. The number of scores in each group goes into one of the four cells of the observed table. The number of scores in cell A is the same number as the answer to the third question in assignment 3: How many of your scores are BOTH high and ALSO early? We know beforehand that 6 scores are early, since the definition of "early" is "in the first half of the data", that is, one of the first six scores in the time-ordered list. So, the next question is "Of the 6 scores that are early, how many of them are high?" The answer must be 6 or 0 or some whole number in between. The number in cell A and the number in cell B must sum to 6, since the whole top row is for early scores and there are 6 of them in all. Similarly, the numbers in cells C and D must also add to 6, since the bottom row is for scores that are not early and there are also 6 of them in all.
In assignment 3 (done automatically in the Excel section of this course), the first question and answer relate to the number of "high" scores among your 12 numbers. The definition of "high" is "above the mean." Any score above the mean has a positive Z score. We expect the number of such scores to be about 6 but it could be nearly all of the scores or nearly none of them. It cannot be literally all or none, since it is not possible to have all scores above the mean nor all below.
The numbers in cell A and in cell C must add to the number of high scores in all. Knowing that number from the answer to the first assignment 3 question and knowing the number in cell A, we can subtract cell A from the number of high scores in all to obtain the number in cell C.
The number in cell C can be subtracted from 6 to obtain the number in cell D since cells C & D must add to 6, the number of scores that are not early, that are in the second half of time-ordered list of scores.
Once you have all four cells of the observed table filled in, you can check that the four values sum to 12, the total number of scores in all. Then, the notes on the assignment sheet will help you complete the assignment.