Details

Autor(en) / Beteiligte

• Bryk, Anthony S
• Weisberg, Herbert I

Titel

Use of the nonequivalent control group design when subjects are growing

Ist Teil von

• Psychological bulletin, 1977-09, Vol.84 (5), p.950-962

Ort / Verlag

Washington, etc: American Psychological Association

Erscheinungsjahr

1977

Quelle

EBSCOhost APA PsycARTICLES

Beschreibungen/Notizen

• Many experimental programs aim to accelerate the growth of individuals on some dimension of interest. Typically, a group exposed to the program is compared with a control group. When it is feasible, random assignment of Ss to the program and control groups assures an unbiased comparison between treatments. Without randomization there may be important differences between groups, in terms of pretreatment characteristics and growth potential. In the nonequivalent control group design, pretest and posttest data on both groups are obtained. Statistical methods are used to adjust posttest comparisons, based mainly on pretest information. A variety of statistical techniques have been proposed, but there is much disagreement among methodologists as to which, if any, are adequate. This article examines the adequacy of these techniques, from an individual growth perspective. The performance of various commonly used methods is examined under alternative assumptions about the nature of growth. It is concluded that statistical adjustments are generally inadequate in the face of nonequivalent growth systems across treatment groups. (20 ref)