The following are the cystatin C levels (mg/L) for the patients described in Exercise 15 (A-17).

Cystatin C is a cationic basic protein that was investigated for its relationship to GFR levels. In addition, creatinine levels are also given. (Note: Some subjects were measured more than once.)

Cystatin C (mg/L) Creatinine (mmol/L)

1.78 4.69 0.35 0.14 2.16 3.78 0.30 0.11 1.82 2.24 0.20 0.09 1.86 4.93 0.17 0.12 1.75 2.71 0.15 0.07 1.83 1.76 0.13 0.12 2.49 2.62 0.14 0.11 1.69 2.61 0.12 0.07 1.85 3.65 0.24 0.10 1.76 2.36 0.16 0.13 1.25 3.25 0.17 0.09 1.50 2.01 0.11 0.12 2.06 2.51 0.12 0.06 2.34 Source: Data provided courtesy of D. M. Z. Krieser, M.D.

(a) For each variable, compute the mean, median, variance, standard deviation, and coefficient of variation.

(b) For each variable, construct a stem-and-leaf display and a box-and-whisker plot.

(c) Which set of measurements is more variable, cystatin C or creatinine? On what do you base your answer?