The anion gap is the difference between the number of univalent positive ions (potassium and sodium) and negative ions (chloride) in plasma or urine. Because it was suggested that the urinary anion...

The anion gap is the difference between the number of univalent positive ions (potassium and sodium) and negative ions (chloride) in plasma or urine. Because it was suggested that the urinary anion gap Uag might be a useful indicator of the amount of ammonium ion secreted in the urine, Battle and coworkers† measured urinary ammonium A and Uag in normal subjects, patients with metabolic acidosis due to diarrhea, and patients with relatively common kidney defects. (The data are in Table D-14, Appendix D.) A. Is there any evidence that Uag reflects ammonium in the urine? B. Is it possible to predict ammonium if you know Uag? How precisely? C. Include an evaluation of influential points. D. Does a quadratic model provide a better description of these data than a linear model? Justify your conclusion.

Table D-14