Crossover study

What is a crossover design?

A research design where the subjects get both treatments in sequence. Contrast this with a parallel groups design where some subjects get the first treatment and different subjects get the second treatment. The crossover design represents a special situation where there is not a separate comparison group. In effect, each subject serves as his/her own control. Also, since the same subject receives both treatments, there is no possibility of covariate imbalance. Ideally in a crossover design, a subject is randomly assigned to a specific treatment order. Some subjects will receive the standard therapy first, followed by the new therapy (AB). Others will receive the new therapy first, followed by the standard therapy (BA). Here is an example of a crossover design:

• In Lokken et al (1995), patients received identical oral surgical procedures on two separate occasions. At one surgery, a patient received homeopathic treatment for pain. At the other surgery, a patient received placebo. The researchers measured postoperative pain, bleeding, swelling, and the reduction of the ability to open one's mouth.

This webpage was written by Steve Simon on 2002-10-11, edited by Steve Simon, and was last modified on 2008-07-08. This page needs minor revisions. Category: Definitions, Category: Research designs.

 

http://www.childrens-mercy.org/stats/definitions/crossover.htm

 

Crossover Design:

In randomized trials, a crossover design is one in which each subject receives each treatment, in succession. For example, subject 1 first receives treatment A, then treatment B, then treatment C. Subject 2 might receive treatment B, then treatment A, then treatment C. A crossover design has the advantage of eliminating individual subject differences from the overall treatment effect, thus enhancing statistical power. on the other hand, it is important in a crossover study that the underlying condition (say, a disease) not change over time, and that the effects of one treatment disappear before the next is applied. See also Parallel design.

 

http://www.statistics.com/resources/glossary/c/crossdsgn.php