Title: The concept of control
Course: UGQuants (SSPS) > Section: Causality

The concept of control

To begin to build our model, we need to make a theoretical decision about which variable is prior to any other variable, or in which direction we expect cause and effect to operate. In many situations, we cannot be sure about the temporal order of variables (we may for example have data on several characteristics of economic development, but may not know whether any of these characteristics ’occurred’ before any other ones). In such situations it is necessary to decide which is the most interesting or productive direction or linkage from our research point of view. That is to say, given our research interest, we might want to test a particular sort of causal model or theory about a direction of cause and effect.

However, some variables can never be 'caused' by others (e.g. attitudes cannot 'cause' a person’s current age) and some will take place before others; i.e. there will be a natural temporal ordering of events. But even if we know that one characteristic preceded another and we find that they are correlated to some degree, we cannot be certain that the prior variable is the one ’responsible’ for the variation in the other variable. It could be the case that two variables are correlated, but only because a third variable causes both of them.