Assessments shouldn't allow for perfect scores

Assessments lose their potency when people can attain perfect scores. Rather than helping to discriminate between those who can demonstrate relevant competencies and those who cannot, assessments become a matter of who can makes fewer mistakes under pressure. And if the goal is find those who can perform best (e.g. during an interview, or an admissions exam), it's better if no one is able to attain a perfect score. This way, scores can be used more reliably for comparison, since maximizing achievement can be rewarded more accurately over minimizing errors.

But because for most people's schooling perfect scores were attainable (and often expected), being presented with this kind of assessment can be demoralizing. So, if you're going to use this approach, it's best to set expectations to prevent people from being too hard on themselves while they await your determination.