The tendency to be thorough, dependable, organized, and decisive describes which big five personality factor

The answer is "Conscientiousness".

Conscientiousness is the personality trait of being watchful, or careful. Conscientiousness suggests a longing to complete an undertaking great, and to consider commitments to others important. Conscientious individuals have a tendency to be effective and sorted out instead of nice and sloppy. They show a propensity to show self-control, act obediently, and go for accomplishment; they show arranged as opposed to unconstrained conduct; and they are by and large tried and true. It is showed in trademark practices, for example, being flawless, and precise; likewise including such components as deliberateness, painstaking quality, and consultation (the inclination to think deliberately before acting.)