Home Environment Research Methods in Anthropology: Qualitative and Quantitative Approaches

# CAUSE AND EFFECT

Cause and effect is among the most highly debated issues in the philosophy of knowledge. (See Hollis [1996] for a review.) We can never be absolutely certain that variation in one thing causes variation in another. Still, if measurements of two variables are valid, you can be reasonably confident that one variable causes another if four conditions are met.

• 1. The two variables co-vary—that is, as scores for one variable increase or decrease, scores for the other variable increase of decrease as well.
• 2. The covariation between the two variables is not spurious.
• 3. There is a logical time order to the variables. The presumed causal variable must always precede the other in time.
• 4. A mechanism is available that explains how an independent variable causes a dependent variable. There must, in other words, be a theory.

## Condition 1: Covariation

When two variables are related they are said to co-vary. Covariation is also called correlation or, simply, association.

Association is a necessary but insufficient condition for claiming a causal relation between two variables. Whatever else is needed to establish cause and effect, you can’t claim that one thing causes another if they aren’t related in the first place.

Here are a few interesting covariations:

• 1. Sexual freedom for women tends to increase with the amount that women contribute to subsistence (Schlegel and Barry 1986).
• 2. Ground-floor, corner apartments occupied by students at big universities have a much higher chance of being burglarized than other units in the same apartment bloc (M. B. Robinson and C. E. Robinson 1997).
• 3. When married men and women are both employed full time, they spend the same amount of time in the various rooms of their house—except for the kitchen (Ahrent- zen et al. 1989).

You might think that to establish cause, independent variables would have to be strongly related to the dependent variable. Not always. People all over the world make decisions about whether or not to use (or demand the use of) a condom as a part of sexual relations. These decisions are based on many factors, all of which may be weakly but causally related to the ultimate decision. These factors include: the education level of one or both partners; the level of income of one or both partners; the availability and cost of condoms; the amount of time that partners have been together; the amount of previous sexual experience of one or both partners; whether either or both partners know anyone personally who has died of AIDS; and so on.

Each independent variable may contribute only a little to the outcome of the dependent variable (the decision that is finally made), but the contribution may be quite direct and causal.

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