# Page:Popular Science Monthly Volume 70.djvu/162

The method of using the test was to place the printed list before the subjects and ask them to mark the words that they knew with a plus (${\displaystyle +}$) sign, those that they did not know with a minus (${\displaystyle -}$) sign, and doubtful ones with a question mark (?). The tests which numbered about two thousand were made chiefly upon pupils from the fourth grade up through the high school and university, although a few were made upon younger children. Control tests showed that if the same test was given orally, there was some difference in the words marked as known and unknown. This difference was of course very great in the second and third grades, where a few tests were made, and became less with age, yet it usually amounted even in the case of adults to from one to three per cent. In a few individuals the difference was quite marked.