If we ask the patient attending OPD to evaluate his pain on a scale of 0 (no pain) to 5 (the worst pain), then this commonly applied scale is a

Ratio scale is a type of variable measurement scale which is quantitative in nature. Ratio scale allows any researcher to compare the intervals or differences. Ratio scale is the 4th level of measurement and possesses a zero point or character of origin. This is a unique feature of ratio scale Ref : Internet sources