In an experiment, a causal variable is manipulated actively to measure how it has affected the dependent variable of interest. There can be one or more causal variable and dependent variable.

To illustrate,

O A publishing company prints several cover designs for its advertising text book, and asks the students which cover design do they like the best. This experiment tests the effects on cover design on preference.

O The publishing company prints two different cover designs and sends the advertising book to different book sellers. It then measures the sales for each design. In this experiment, we measure how a cover design affects the sales.

O A butter producer can ask its customers to rate the butter on its taste, spreadability and thickness. The experiment measures the effects of various attributes on product ratings.

O A music system can have four different price levels, four different brand names, two different power sources (mains plus battery) and two different sources of music — tape and radio. The consumers are to rank these sixty four combinations from most preferred to least preferred. The attributes and their effect on preference was measured.

The experimental variables in all the above examples have certain outcomes, i.e sales, preference which are dependent variables. Outcomes are produced since the experimental variables are manipulated. It is this active manipulation which makes the studies an experiment.

Experiments can take many forms. They can be conducted at homes, in shops, in marketplace. The manipulations can be physical or hypothetical. There can be any number of manipulations. There can be a measurement of any number of dependent variables. The unit of measurement can be an individual, household, companies, markets etc.