%0 Journal Article %T Measuring the impact of an instructional laboratory on the learning of introductory physics %A Carl Wieman %A N. G. Holmes %J Physics %D 2015 %I arXiv %X We have analyzed the impact of taking an associated lab course on the scores on final exam questions in two large introductory physics courses. Approximately a third of the students who completed each course also took an accompanying instructional lab course. The lab courses were fairly conventional, although they focused on supporting the mastery of a subset of the introductory physics topics covered in the associated course. Performance between students who did and did not take the lab course was compared using final exam questions from the associated courses that related to concepts from the lab courses. The population of students who took the lab in each case was somewhat different from those who did not enroll in the lab course in terms of background and major. Those differences were taken into account by normalizing their performance on the lab-related questions with scores on the exam questions that did not involve material covered in the lab. When normalized in this way, the average score on lab-related questions of the students who took the lab, in both courses, was within 1% of the score of students who did not, with an uncertainty of 2%. This result raises questions as to the effectiveness of labs at supporting mastery of physics content. %U http://arxiv.org/abs/1506.02969v2