“…5 However, Guthrie and Slifko have shown that random selection of entries, rather than keys, yields results closer to actual experience but with a higher number of entries per reply. 6 For example, they found on retrieving from a file of 857,725 records using a 4, 5 (four characters of main entry, five characters of title) key tl1at when the basis of the search was random keys there was one entry per reply 81.3 percent of the time, but when the basis was random records, there was one entry per reply 55.7 percent of the time.…”