So as a rough estimate, their vocabularies would have increased by twenty words, from, say, 11,000 words to 11,020, or from 17,000 to 17,020. An improvement, perhaps, but hardly enough to merit comment. There may be cases in which learning what is specifically on the test constitutes substantial improvement, but the general conclusion remains that even inferences about improvement are undermined by certain types of test preparation that focus on the specific sample included in the test.
