In Katia's Remedial Mathematics Study, She Collected Pretest Data from a Group

Multiple Choice

In Katia's remedial mathematics study, she collected pretest data from a group of participants. She divided the participants into three groups. One group received no treatment, one group received instruction by a teacher-delivered intervention, one group received peer tutoring on the same problems. After the intervention she tested their math skills. With which validity threat should Katia be most concerned?

A) Maturation
B) Testing
C) Instrumentation
D) Mortality