JOURNAL o* CHEMICAL EDUCATION
896
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J a y , 1927
The percentage of pupils correctly answering a given question seems to d>pend not only on their absolute ability to do so, but partly upon the general setting and partly upon the position of the question in that setting. In general, test results show that the later an item is placed in a test the smaller is the percentage of children correctly answering it.a The reason usually given for this is that tests are built so that questions become more difficult toward the end. This may be one reason, but the illustrative cases given above show that other factors operate; for iOyo of pupils knew the formula for ammonium hydroxide when placed early in a test, but only 60% knew it 15 minutes later, when they were near the end of the same test. It would appear that, even if ample time is given, some children do not get through so far as to attempt some questions which they can answer. This must have happened to 10yoof the children who took Glenn's test No. 12. These results illustrate the point made, namely, that one cannot justly say that a certain percentage of children cannot answer a particular question without stating the conditions under which that question was given. The fact that 31% of students fail to complete and balance the HCI = in a specific circumstance (in the Iowa Test) equation KOH does not warrant the general assumption that "about a third of the group learned nothing of equation writing while in high school."
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Conclusion Criticisms of present results and practice in the teaching of high-school chemistry are becoming increasingly numerous. Test methods and statistical treatment of results are increasingly used as means for obtaining grounds for criticism. The above analysis of presented results of such usage appears timely a t this stage, for if testing procedures are not to defeat their own ends and fall into disrepute, they must be rigidly exact and scrupulously fair to present teachers and students. a Mr. Glenn's figures show this v~wydefinitely. See Stoddard's figures in University of Iowa Studies in Education, Vol 111, No. 2, pp. 44-52.
Corn Uses Nitrogen Captured by Bacteria. Will corn come to rival clover as a nitrogen-catching crop? The activity of the helpful bacteria that live in the little lumps or nodules on clover and pea and alfalfa roots has long been known. Now, a t the meeting of the First International Soil Science Congress held recently, Dr. Georges Tmffaut and Dr. N. Bezssonoff, of Versailles, France, advanced data which tend to prove that other plants, without definite root nodules, are able to feed soil bacteria, which in their turn capture nitrogen from the air and so benefit their benefactors. The two experimenters stated that they were unable t o grow ordinary corn in white sand from which every trace of nitrogen had been chemically removed, and to which no nitrogenous fertilizers were added. They are of the opinion that the corn roots supply some kind of needed food material to the bacteria on which the latter can live while they work a t their business of capturing nitrogen from the air.-Science Semke
