An often-voiced concern is that candidates memorize item content, and then share the information with colleagues. Candidates so forewarned of what is on a test may have an unfair advantage, and might be able to pass the test without having the required level of knowledge and skill. To determine if candidates are able to gain an unfair advantage in this way, a systematic study was conducted.
 
The study examined item p-values across exam administrations. The p-value is the percent of candidates who answer an item correctly. If the p-values of items that appear on more than one examination increase by less than 10% from one exam to the next, there is a low probability that individual candidates are benefiting from items being leaked.
 
The p-values of items used on consecutive exams were compared. The table below shows the results. For all five examinations, the majority of the common items did not show p-value increases of more than 10%. Furthermore, even though some of the tests included a large number of carryover items, the items that had higher p-values (easier) were a very small percentage of the total number of items on the second test.
 
Thus, the use of common items on certification examinations does not seem to increase the percent of candidates who answer the item correctly. This makes one wonder about the efficiency of the networks of individuals who supposedly memorize items during a test to share with their colleagues. Perhaps their memories are not terribly accurate, their colleagues are not helped by the information, or misinformation is actually transmitted.