Chapter 9

• Between-subjects design


  A design in which different subjects take part in each condition of the experiment.
• Block randomization

  • A process of randomization that first creates treatment blocks containing one random order of the conditions in the experiment.
  • Subjects are then assigned to fill each successive treatment block.
• Control condition


  A condition in which subjects receive a zero value of the independent variable.
• Control group


  The subjects in a control condition.
• Effect size


  A statistical estimate of the size or magnitude of the treatment effect(s).
• Experimental condition

  • A treatment condition in which the researcher applies a particular value of an independent variable to subjects and then measures the dependent variable.
  • In an experimental group–control group design, the group that receives some value of the independent variable.
• Experimental design


  The general structure of an experiment (but not its specific content).
• Experimental group


  The subjects in an experimental condition.
• Multiple-groups design


  A between-subjects design with one independent variable, in which there are more than two treatment conditions.
• Multiple-independent-groups design


  The most commonly used multiple-groups design in which the subjects are assigned to the different treatment conditions at random.
• Pilot study


  A mini-experiment using only a few subjects to pretest selected levels of an independent variable before conducting the actual experiment.
• Placebo group

  • In drug testing, a control condition in which subjects are treated exactly the same as subjects who are in the experimental group, except for the presence of the actual drug.
  • The prototype of a good control group.
• Precision matching


  Creating pairs whose subjects have identical scores on the matching variable.
• Random assignment


  The technique of assigning subjects to treatments so that each subject has an equal chance of being assigned to each treatment condition.
• Range matching


  Creating pairs of subjects whose scores on the matching variable fall within a previously specified range of scores.
• Rank-ordered matching

  • Creating matched pairs by placing subjects in order of their scores on the matching variable.
  • Subjects with adjacent scores become pairs.
• Two-experimental-groups design


  A design in which two groups of subjects are exposed to different levels of the independent variable.
• Two-groups design


  The simplest experimental design used when only two treatment conditions are needed.
• Two-independent-groups design


  An experimental design in which subjects are placed in each of two treatment conditions through random assignment.
• Two-matched-groups design


  An experimental design with two treatment conditions and with subjects who are matched on a subject variable thought to be highly related to the dependent variable.