Question 2 of 37 1 Points Which of the following is the definition of the "experimental mortality" threat to internal validity? A. occurrences during the course of a study extraneous to the independent (treatment) variable O B. group differences on some relevant variable before experimental treatment O C. nonrandom loss of subjects during a study D. changes in measurement procedures during a study E. biological and psychological processes that naturally occur within subjects during the course of a study Reset Selection Mark for Review What's This