Simpson's paradox can also be illustrated using the 2-dimensional vector space.[21] A success rate of p q {\displaystyle \textstyle {\frac {p}{q}}} (i.e., successes/attempts) can be represented by a vector A → = ( q , p ) {\displaystyle {\overrightarrow {A}}=(q,p)} , with a slope of p q {\displaystyle \textstyle {\frac {p}{q}}} . A steeper vector then represents a greater success rate. If two rates p 1 q 1 {\displaystyle \textstyle {\frac {p_{1}}{q_{1}}}} and p 2 q 2 {\displaystyle \textstyle {\frac {p_{2}}{q_{2}}}} are combined, as in the examples given above, the result can be represented by the sum of the vectors ( q 1 , p 1 ) {\displaystyle (q_{1},p_{1})} and ( q 2 , p 2 ) {\displaystyle (q_{2},p_{2})} , which according to the parallelogram rule is the vector ( q 1 + q 2 , p 1 + p 2 ) {\displaystyle (q_{1}+q_{2},p_{1}+p_{2})} , with slope p 1 + p 2 q 1 + q 2 {\displaystyle \textstyle {\frac {p_{1}+p_{2}}{q_{1}+q_{2}}}} .