The negative direction occurs when the proposed feature is absent and the judgment is absent.
In the same intact circuit, opening the switch extinguishes the bulb. Repeating both states strengthens the argument, because the presence and absence have each been examined.
The other relevant conditions must stay constant. If the power supply also fails, the observations do not isolate the switch as the causal factor.
Opening interactive controls...
Analogy: Original and New Cases, Common Cause, Co-variation and Elimination
The negative direction occurs when the proposed feature is absent and the judgment is absent.
In the same intact circuit, opening the switch extinguishes the bulb. Repeating both states strengthens the argument, because the presence and absence have each been examined.
The other relevant conditions must stay constant. If the power supply also fails, the observations do not isolate the switch as the causal factor.