Low power design is a critical concern and metric for integrated circuits. During scan based manufacturing test, electric power dissipation becomes even more critical as the chip may not have been designed to tolerate excessive switching during scan test. Excessive electric power dissipation during scan test can result in excessive voltage variations, reduced noise margins and other signal integrity issues which could invalidate the test or may lead to premature chip failure. Power dissipation during test is minimized by selecting particular values for the unused care-bits in values of the test vectors on a probabilistic basis to minimize switching, while preserving test vector quality.