WAEC 2018 · Paper 2 · Q6

Geography	6	5	4	3	2	7	1
Economics	7	6	2	4	1	5	3

The table shows the ranks of marks scored by 7 candidates in Geography and Economics tests.

Worked solution (try it first)

The table already gives ranks.
$d$ = Geography − Economics: $-1, -1, 2, -1, 1, 2, -2$ .
$\sum d^2 = 1 + 1 + 4 + 1 + 1 + 4 + 4 = 16$ .
$\rho = 1 - \dfrac{6 \times 16}{7 \times 48}$
$= 1 - \dfrac{96}{336}$
$= \dfrac57$
$\approx 0.7143$ .