Different endeavors have been made to create a scientific categorization of levels of estimation. The psychophysicist Stanley Smith Stevens characterized ostensibly, ordinal, span, and proportion scales. Ostensibly estimations don't have significant position request among values, and grant any coordinated (injective) change. Ordinal estimations have uncertain contrasts between successive qualities, however have a significant request to those values, and grant any request safeguarding change. Span estimations have significant distances between estimations characterized, yet the zero worth is erratic (as for the situation with longitude and temperature estimations in Celsius or Fahrenheit), and grant any direct change. Proportion estimations have both a significant zero worth and the distances between various estimations characterized, and license any rescaling change