|Table of contents|
2 Purchase Laboratory
3 Test Markets
4 Experimental research designs
5 See also
6 Lists of related topics
One of the most important requirements of experimental research designs is the necessity of eliminating the effects of spurious, intervening, and antecedent variables. In the most basic model, cause (X) leads to effect (Y). But there could be a third variable (Z) that influences (Y), and X might not be the true cause at all. Z is said to be a spurious variable and must be controlled for. The same is true for intervening variables (a variable in between the supposed cause (X) and the effect (Y)), and anteceding variables (a variable prior to the supposed cause (X) that is the true cause). When a third variable is involved and has not been controlled for, the relation is said to be a zero order relationship. In most practical applications of experimental research designs there are several causes (X1,X2,X3). In most designs only one of these causes is manipulated at a time.
A true experimental design requires an artificial environment so as to control for all spurious, intervening, and antecedent variables. A purchase laboratory approaches this ideal. Subjects are given money, script, or credit to purchase products in a simulated store. Researchers modify one variable at a time (for example; price, packaging, shelf location, size, or competitorsí offerings) and determine what effect that has on sales volume. Internet based purchase labs (called virtual purchase labs) are becoming more common.
Quasi-experimental designs control some, but not all, of the extraneous factors. A test market is an example of this. A new product is typically introduced in a select number of cities. These cities must be representative of the overall national (or international) population. They should also be relatively unpolluted by outside influences (for example : media from other cities). The marketer has some control over the marketing mix variables, but almost no control over the broader business environment variables. Competitors could change their prices during the test. Government could change the level of taxes. New competing products could be introduced. An advertising campaign could be initiated by competitors. Any of these spurious variables could contaminate the test market.
Experimental research designs
In an attempt to control for extraneous factors, several experimental research designs have been developed, including:
Lists of related topics