The ratio level of measurement is the highest level of measurement, encompassing all properties of nominal, ordinal, and interval scales, with the addition of a true zero point. This true zero represents the complete absence of the measured quantity, such as zero Kelvin indicating no kinetic energy, or zero money indicating no money. Because of the true zero, it allows for meaningful statements about the ratios of scores. For example, while one cannot say someone with an IQ of $140$ is twice as intelligent as someone with an IQ of $70$ because IQ is an interval scale, one can say that someone with $6$ siblings has twice as many as someone with $3$ because the number of siblings is measured at the ratio level. Additionally, ratio-level measurement permits any indicators of central tendency to be computed, including the mean, median, or mode.