One Group Design 1. One group posttest design This type of design is the simplest ones. It is commonly called pre-experimental design. Students in such type of experiment no formal comparison is possible for there is no second group with comparison can be made. Let us illustrate with an example suppose a teacher treats 10 students who are addicted to smoking in a period of three months. At the end of the period six students give up smoking. Such type of designs do not control any of the sources of invalidity.
19 2. One group pretest-posttest design This is also simple design and is considered to be a rather poor design though better than one group posttest design. In this design the experimenter first tests a group on some aspects of behhaviour and then gives special treatment. He statistically analyses the data and calculates the difference between the pretest and posttest scores of the group. The paradigm of the design is as follows Pretest Independent variable Posttest TX T Example, Suppose in the beginning of the semester, we administer test of educational psychology to students of MA education and then we teach them the subject throughout the semester. At the end of the semester we administer posttest (T, and find out the difference between the scores on the initial and final tests.