One of the methods used in psychological research is correlation. The word correlation means the relationship between two factors. There are three types of correlations: positive, negative or without correlation. The positive correlation is when the variables increase or decrease at the same time; the negative is when the variable increases while the other decreases; and without correlation is when two variables are not correlated, that is, the change in one variable does not affect the other.
In the area of psychological research, correlation is used when the psychologist wants to know what factors or variables are connected to each other. In this way, the correlational method searches for different variables that interact with each other so if there is evidence that one of the variables changes, the psychologist can know how the other variable which is directly related will change. In other words, the psychologist can study one of the variables and the relationship and impact on the variable. For example, the psychologist can study the school performance and family environment in a group of children to determine their relationship.
There are two reasons why psychologists use this method: they do not believe that the relationship between the variables is accidental and; the other is the causal statistics between the variables independently, which is impossible and not very ethical.
Within the corrective method, there are three types of research: natural observation which the psychologist observes and records the variable within natural environment, without any interference; the second, is surveys and questionnaires, which is chosen by a random group of participants to collect the information; and finally, information analysis is when the researcher analyzes large amounts of data collected previously by other researchers.
However, psychologists are cautions when analyzing the relationships that occur between two variables, which should take into account two possible sources of error: problem of directionality since they can not show which variable occurred first and which occurs second, and the problem of the third variable is when psychologists can not know if an unobserved variable is related to each of the other variables.
Therefore, the characteristic of the corrective method is that there are two treated variables measured without being manipulated and the results are true regardless of the type of variable.