Validity and reliability are two critical concepts in implementing effective outcome measurement systems. These concepts can be illustrated through the example of a bathroom scale. Let’s say Jennifer weighs herself every day and finds that the scale always reads 150 pounds. Assuming she is not losing or gaining weight, and that she actually does weigh 150 pounds, then the scale is valid and reliable. It’s valid because it displays an accurate reading, and it’s reliable because it displays this reading each time it’s used. The scale could be reliable without being valid. For example, if Jennifer’s weight is displayed each day as 135 pounds, then the scale is not providing a valid reading because the number is not accurate. It doesn’t measure Jennifer’s true weight. If, however, the scale always reads 135 pounds, and she is not gaining or losing weight, then it is still reliable because it reflects a consistent reading.