Put simply, the reliability of a measure tells you how precisely you are measuring something, whereas the validity of a measure tells you how accurate the measure is. Notice that this concept of relia...Put simply, the reliability of a measure tells you how precisely you are measuring something, whereas the validity of a measure tells you how accurate the measure is. Notice that this concept of reliability is different from the question of whether the measurements are correct (the correctness of a measurement relates to its validity).