Sociologists observe the social "organism" as biological scientists study living organisms. The individual is a contributing and an affective part of a systematic whole. In complex societies, there may be nested systems, or multiple systems inside of larger systems. An individual may be a member of a religious system, a corporate system, and a family system, which operate within nested social systems: the community, the county, the state, and so on.
In studying and testing the relationships between individuals, systems and the larger systems, sociologists have refined "cause and effect" as a tool. There are some basic rules that are adhered to in developing studies of cause and effect, which have also stood the test of time:
First, the cause has to come before the effect. This may sound simple, but in many cases, it is no where as simple as it looks. There may be other cause and effect relationships going on at the same time. These are called "intervening variables". There may be an ongoing seasonal or cyclical activity, where looking at the variables at one single point in time, then another, results in observations where the cause appears to come first, then the effect appears to come first. Actually there is cause, then effect, then cause, then effect on a steady and ongoing basis.
As a result, the process of confirming that the cause comes before the effect includes isolating only one cause and one effect, then confirming beyond a doubt that the cause occurs, or occurred first. This is called "Establishing Temporal Precedence".
Cause, or variable "A" is the "Causative Variable". The variables that are affected by the causative variable are called "Dependent Variables".
Second, the type of relationship, or what does change in the causative variable do to the second variable? The answer to that question gives the identity of the effect by establishing that there is "Co variation Of The Cause And Effect". There are also different types of relationships that are direct, inverse, one to one, one to many, or recursive.
Simple direct co variations mean that change in the first variable causes the same change in the second variable. Having more money causes people to spend more money. Increase in variable A causes increase in variable B (spending). A decrease in money causes a decrease in spending. Decrease in variable A causes decrease in variable B.
But, some causes can affect many variables. Having more money (variable A) can be dealt with in many ways: Variable B=spending. Variable C=saving. Variable D=giving away. This is called a "One To Many" relationship, where change in one causative variable can cause changes in many dependent variables. We operate the dishwasher one time, but we change many items from dirty to clean.
Some causes have a Recursive affect: Person A hits person B, causing person B to change from a peaceful person into a violent person who desires to hit Person A. Person A gets hit. In the recursive relationship the causative variable causes a change in the dependent variable. The dependent variable then become a causative variable.
Third, the sociologist must establish "Internal Validity" by confirming that no other plausible explanation exists for the the change in variable B. This is the most challenging part of establishing cause and effect. Some other variable or event may be causing change in variable B. This is called the "missing variable". Variable B may not be changing as the result of temporal causation at all. Variable A may not be changing at all. Variable B may not change every time that Variable A changes.
The most complex example of establishing cause and effect is in program development, execution and evaluation. There are many threats to the group process, and thus to proving, for example, that a program for increased tutoring will result in more children graduating from high school on time. It is not difficult to immediately identify possible external, intervening, invisible, missing, and interfering variables, when it comes to proving that teenagers graduated or did not graduate on time because of the extra tutoring.