It is certain that they made plenty of mistakes, introducing a large degree of random error into the measurements. (oceanmotion.org)
It's true that there is more random error in measuring gains in test scores than in measuring the level of test scores. (educationnext.org)
In this case, having more students reduces random error among middle school teachers, but, as the baseball analogy suggests, this does not increase reliability. (carnegieknowledgenetwork.org)