WAEC 2018 · Paper 2 · Q5

Cooking oil	A	B	C	D	E	F	G	H
$X$	8	5	1	7	2	6	3	4
$Y$	6	3	4	8	5	7	1	2

Two panels of judges, $X$ and $Y$ , rank 8 brands of cooking oil as shown.

Worked solution (try it first)

The judges' values are already ranks.
$d = X - Y$ : $2, 2, -3, -1, -3, -1, 2, 2$ .
$\sum d^2 = 4 + 4 + 9 + 1 + 9 + 1 + 4 + 4$
$= 36$ .
$\rho = 1 - \dfrac{6 \times 36}{8 \times 63}$
$= 1 - \dfrac{216}{504}$
$= \dfrac47$
$\approx 0.5714$ .