Answer to Question 1
A within-subjects design involves repeated measures because with each treatment the same subject is measured. In contrast, a between-subjects design measure each dependent variable only once for each subject. Between-subjects designs are usually advantageous although they are usually more costly. The validity of between-subjects designs is usually higher because by applying only one treatment combination to one subject, demand characteristics are greatly reduced. When a subject sees multiple conditions, he or she is more likely to guess what the study is about. In addition, statistical analyses of between-subjects designs are simpler than within-subjects designs. This also means the results are easier to report and explain to management.
Answer to Question 2
The term demand characteristic refers to an experimental design element that unintentionally provides subjects with hints about the research hypothesis. Knowledge of the experimental hypothesis creates a confound known as a demand effect. Demand characteristics are aspects of an experiment that demand (encourage) that the subjects respond in a particular way, hence being a source of systematic error. Ways of reducing demand characteristics include the following:
(1) Use an experimental disguise.
(2) Isolate experimental subjects.
(3) Use a blind experimental administrator.
(4) Administer only one experimental treatment level to each subject.
The experimental approach used by Masui and Markert to identify cyclin and cyclin-dependent kinase (
Connell's experimental manipulation of species indicated the presence of competition.
The theoretical design of nature reserves, based on the tenets of island biogeography.
Advantages and Disadvantages of Managed Care
Basic Design of the Driving and Cell Phone Distraction Experiment
Suppose that we have a sample space with five equally likely experimental outcomes: E1, E2, E3, ...