Before revision: It can be used if there are concerns that the treatment might be sensitized by the pre-test.Introduction to Research in Education by Donald Ary, Lucy Jacobs, Christine Sorensen The four groups have four different experiences: Pre-test, treatment, post-test Pre-test, no treatment, post-test Treatment, post-test No treatment, post-test The effectiveness of the treatment can be evaluated by comparisons between groups 1 and 2 and between groups 3 and 4.
After revision: It can be used if there are concerns that the treatment might be sensitized by the pre-test.Introduction to Research in Education by Donald Ary, Lucy Jacobs, Christine Sorensen The four groups have four different experiences: Pre-test, treatment, post-test Pre-test, no treatment, post-test Treatment, post-test No treatment, post-test The effectiveness of the treatment can be evaluated by comparisons between groups 1 and 3 and between groups 2 and 4.