A high school teacher conducted a test of a new approach to teaching math. Students were given a pretest when their math class began and a posttest at the end of the semester. The students' math performance improved. The teacher learned near the end of the semester, however, that in their science classes the students were using new computer software that included much of the math the teacher covered in his course. Which threats to internal validity does the new computer software represent? selection regression history testing?

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The introduction of new computer software in the science classes poses a potential threat to the int... View the full answer