Orthogonal array testing is a systematic and statistical way of a black box testing technique used when number of inputs to the application under test is small but too complex for an exhaustive testing.
OAT, is a systematic and statistical approach to pairwise interactions.
Executing a well-defined and a precise test is likely to uncover most of the defects.
100% Orthogonal Array Testing implies 100% pairwise testing.
If we have 3 parameters, each can have 3 values then the possible Number of tests using conventional method is 3^3 = 27 While the same using OAT, it boils down to 9 test cases.