6. Spearman Rank Correlation: Calcium Tests Random collections of nine different solutions of a calcium compound were given to two laboratories A and B. Each laboratory measured the calcium content (in mmol per liter)

and reported the results. The data are paired by calcium compound (Reference: Journal of Clinical Chemistry and Clinical Biochemistry, Vol. 19, pp. 395–426).

Compound 1 2 3 4 5 6 7 8 9 Lab A 13.33 15.79 14.78 11.29 12.59 9.65 8.69 10.06 11.58 Lab B 13.17 15.72 14.66 11.47 12.65 9.60 8.75 10.25 11.56

(a) Rank-order the data using 1 for the lowest calcium reading. Make a table of ranks to be used in a Spearman rank correlation test.

(b) Use a 5% level of significance to test for a monotone relation (either way) between ranks.

Interpret the results.