Analyze each of the following arguments in terms of the variation of the “phenomena” to show how they follow the pattern of the method of concomitant variation:

Potassium in the urine is known to reflect potassium intake from the diet. At the Prosserman Center for Health Research in Toronto, Dr. Andrew Mente and colleagues analyzed urinary potassium as a useful clinical marker of a healthy diet. They collected urine samples from hundreds of patients and separately calculated the quality of their diets. The results were striking: as urinary potassium increased there was a steady and significant increase in diet quality score, as well as a steady decrease in body mass, blood pressure and heart rate. “This urinary marker,” said Dr. Mente, “is a simple,
objective, universally available measure of diet quality.”
—Urology/Nephrology News, 20 November 2006