Russel-Research-Method-in-Anthropology

The Foundations of Social Research 61
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 covary—that is, as scores for one variable increase or
decrease, scores for the other variable increase or 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 covary. 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 (Robinson and 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
(Ahrentzen et al. 1989).
You might think that in order 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