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SAI INTERNATIONAL SCHOOL

Statistics for Economics

Class-XI

CHAPTER - 11

Correlation analysis

(Module-66 )

Computation of Rank Correlation

When Ranks are equal and Repeated

Repeated ranks

When two or more items have equal values (i.e., a tie) it is difficult to give ranks to
them. In such cases the items are given the average of the ranks they would have
received. For example, if two individuals are placed in the 8 place, they are given
th
the rank [8+9] / 2 = 8.5 each, which is common rank to be assigned and the next
will be 10; and if three ranked equal at the 8th place, they are given the rank [8 + 9
+10] /3 = 9 which is the common rank to be assigned to each; and the next rank

will be 11.

In this case, a different formula is used when there is more than one item having

the same value.

th
where m i is the number of repetitions of i rank
Example Compute the rank correlation coefficient for the following data of the

marks obtained by 8 students in the Commerce and Mathematics.