The proportion of weight lost is a ratio scale, since zero represents on weight lost and each score represents an equal amount of weight lost. However, this is a good example of how the measure may not map well onto other psychological concepts. For example, it is relatively easy to lose 5% of your body weight, but usually takes more than four times the effort to lose 20% of your body weight. Furthermore, the amount of effort needed to lose a given proportion of your body weight will usually depend on your initial weight. Nevertheless, this is still a ratio scale.