Nothing in this world is perfect, and that includes intelligence tests. Though they are a useful tool for a variety of purposes, intelligence tests – and other tests that measure g – sometimes produce inaccurate scores for individual examinees. And inaccurate scores can lead to incorrect decisions. Sometimes the consequences of using an inaccurate test score can have a lasting impact on an examinee, such as in college admissions testing, diagnosing a disability, or employee selection or promotion. Under extreme circumstances, test score accuracy can be a matter of life and death. After the US Supreme Court ruled that executing someone with an intellectual disability was unconstitutional in 2002 (Atkins v. Virginia), accurately estimating the IQ score of an inmate with an intellectual disability can save that person’s life.