where a0,a1,an are coefficients to be determined by regression and n is the degree of the polynomial. Typically, the degree of the polynomial is that which provides the best fit to the data when using a least-squares objective function. P5I . 8. Table 5.8 presents data showing vapor pressure vs. temperature for carbon dioxide. In a design problem, the data needs to be correlated using algebraic expressions which can provide the pressure P(kPa) as a function of temperature T(K). A simple polynomial could be used as an empirical modeling equation in the form P=a0+a1T+a2T2+a3T3++anTn