Purpose and Characteristics of Experimental Research Experiment: a way of learning something by varying some condition and observing the effect on something else. Experimental Research: a procedure for investigating cause-and-effect relationships by randomly assigning subjects to groups in which one or more independent variables are manipulated. Characteristics of Experimental Research: 1. Statistical equivalence of subjects in different groups, usually achieved by random assignment of subjects 2. Comparison of two or more groups or sets of conditions 3. Direct manipulation of at least one independent variable 4. Measurement of each dependent variable 5. Use of inferential statistics 6. Design that provides maximum control of extraneous variables Pre-Experimental Designs: without one or more of six characteristics Notation: R = randomization O = observation, a measure that records observations of a pre-or posttest X = treatment conditions (subscripts 1 through n indicating different treatments A,B,C = groups of subjects, or, for single-subject designs, baseline or treatment conditions A. One-Group Posttest-Only Design X O Time
B. One-Group Pretest-Posttest Design O1 X O2 Time A university professor has received a grant to conduct inservice workshops for teachers on the topic of mainstreaming. One objective of the program is to improve the attitudes of the teachers toward mainstreaming of exceptional children C. Posttest-Only with Nonequivalent Groups Group Treatment Posttest A X O B O Time D. Expanded Posttest-Only with Nonequivalent Groups Design A X1 O1 B X2 O2 Time True Experimental Designs: A. Pretest-Posttest Control Group Design Randomization Group Pretest Treatment Posttest A O1 X O2 R B O1 O2 Time B. Pretest-Posttest Comparison Group Design Randomization Group Pretest Treatment Posttest A O1 X1(Method 1) O2 R B O1 X2(Method 2) O2 C O1 X3(Method 3) O2 Time
C. Pretest-Posttest Control /Comparison Group Design Randomization Group Pretest Treatment Posttest…