A psychologist had a random sample of 22 students.He grouped them into 11 pairs.In each pair,one student was taught by method A and other by method B and were examined after the completion of the course.The marks obtained by them are tabulated below :

Question

Pair :	1	2	3	4	5	6	7	8	9	10	11
A :	24	29	18	14	30	19	27	31	20	28	11
B :	37	35	16	26	23	27	19	20	15	11	21

Find the Kendall's rank correlation coefficient.