When patients are unable to eat for long periods, they must be given intravenous nutrients, a process called parenteral nutrition. Unfortunately, patients on parenteral nutrition show increased...

When patients are unable to eat for long periods, they must be given intravenous nutrients, a process called parenteral nutrition. Unfortunately, patients on parenteral nutrition show increased calcium loss via their urine, sometimes losing more calcium than they are given in their intravenous fluids. Such a calcium loss might contribute to bone loss as the body pulls calcium out of bones to try to keep the calcium level in the blood within the normal range. In order to better understand the mechanisms of the calcium loss in the urine, Lipkin and coworkers* measured urinary calcium UCa and related it to dietary calcium DCa , dietary protein level Dp , urinary sodium UNa , and glomerular filtration rate Gfr , which is a measure of kidney function. These data are in Table D-5, Appendix D. Using simple (univariate) regression analyses, is there any evidence that UCa relates to any of these four other variables? What can you tell about the relative importance of these four variables in determining UCa?

Table D-5