<p>Fwiw, Bluebayou’s explanations are right on the money. On the other hand, Echelon32 is incorrect. </p>
<p>The bottom line is that there are no difference among the dates and that the population that takes one particular test has NO influence. One could take the test with 1,000,000 hard drinking and hard guessing monkeys, and it would make any difference on the score. Of course, the use of the experimental and equating section would be … quite minimal. :D</p>