Causal Research Design
Causal Research Design: Experimentation
Concept of Causality
A statement such as "X causes Y " will have the following meaning to an ordinary person and to a scientist.
____________________________________________________ Ordinary Meaning Scientific Meaning ____________________________________________________ X is the only cause of Y. X is only one of a number of possible causes of Y.
X must always lead to Y (X is a deterministic cause of Y).
It is possible to prove that X is a cause of Y.
The occurrence of X makes the occurrence of Y more probable (X is a probabilistic cause of Y).
We can never prove that X is a cause of Y. At best, we can infer that X is a cause of Y.
Conditions for Causality
Concomitant variation is the extent to which a cause, X, and an effect, Y, occur together or vary together in the way predicted by the hypothesis under consideration. The time order of occurrence condition states that the causing event must occur either before or simultaneously with the effect; it cannot occur afterwards. The absence of other possible causal factors means that the factor or variable being investigated should be the only possible causal explanation.
Definitions and Concepts
Independent variables are variables or alternatives that are manipulated and whose effects are measured and compared, e.g., price levels. Test units are individuals, organizations, or other entities whose response to the independent variables or treatments is being examined, e.g., consumers or stores. Dependent variables are the variables which measure the effect of the independent variables on the test units, e.g., sales, profits, and market shares. Extraneous variables are all variables other than the independent variables that affect the response of the test units, e.g., store size, store location, and competitive effort.
Experimental Design
An experimental design is a set of procedures specifying
the
Concept of Causality
A statement such as "X causes Y " will have the following meaning to an ordinary person and to a scientist.
____________________________________________________ Ordinary Meaning Scientific Meaning ____________________________________________________ X is the only cause of Y. X is only one of a number of possible causes of Y.
X must always lead to Y (X is a deterministic cause of Y).
It is possible to prove that X is a cause of Y.
The occurrence of X makes the occurrence of Y more probable (X is a probabilistic cause of Y).
We can never prove that X is a cause of Y. At best, we can infer that X is a cause of Y.
Conditions for Causality
Concomitant variation is the extent to which a cause, X, and an effect, Y, occur together or vary together in the way predicted by the hypothesis under consideration. The time order of occurrence condition states that the causing event must occur either before or simultaneously with the effect; it cannot occur afterwards. The absence of other possible causal factors means that the factor or variable being investigated should be the only possible causal explanation.
Definitions and Concepts
Independent variables are variables or alternatives that are manipulated and whose effects are measured and compared, e.g., price levels. Test units are individuals, organizations, or other entities whose response to the independent variables or treatments is being examined, e.g., consumers or stores. Dependent variables are the variables which measure the effect of the independent variables on the test units, e.g., sales, profits, and market shares. Extraneous variables are all variables other than the independent variables that affect the response of the test units, e.g., store size, store location, and competitive effort.
Experimental Design
An experimental design is a set of procedures specifying
the