Final answer:
Conscientiousness is the Big 5 personality trait that is the strongest predictor of job performance, as it includes critical characteristics such as self-discipline and reliability in a work context.
Step-by-step explanation:
The Big 5 personality traits are a popular model in psychology for describing human personalities. Based on extensive research into the predictive power of these traits for job performance, conscientiousness has been identified as the strongest predictor. This trait encompasses qualities such as competence, self-discipline, thoughtfulness, and a goal-directed behavior, all of which are highly relevant in a professional setting. High levels of conscientiousness correlate with an employee who is hardworking, reliable, and likely to perform well at work.