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On the proper use of the Pearson correlation coefficient: Checking assumptions through an example applied to health sciences

Abstract:

The checking of the assumptions on which the use of the Pearson correlation coefficient is based, is usually a task in which many errors are committed. Although the process that leads to its calculation and interpretation is simple, the task of verifying conditions such as bivariate normality or the absence of outlier is not so easy, probably because this requires the implementation of multivariate techniques. This review intends to serve as guidance to health sciences researchers, who will surely find situations in which this statistical tool should be used. The article is based on a prevalence study of metabolic syndrome carried out in the Maracaibo city, Venezuela. The main objective is to show by this example the appropriate way to verify the assumptions linked to this coefficient, not forgetting the due theoretical argument that supports them. The mathematical aspect is discarded in order to get the benefits of using computers power, for which the open source R-Studio program is used in each and every one of the processing, plotting and computation activities. The dataset used in the development of the problem are provided, as well as the scripts that activate the functions of the package with the purpose that the reader can reproduce the analysis and compare the results. All this information can be consulted and downloaded from an open access repository.