NIST/ITL StRD Dataset Name: Rat43 (Rat43.dat) File Format: ASCII Starting Values (lines 41 to 44) Certified Values (lines 41 to 49) Data (lines 61 to 75) Procedure: Nonlinear Least Squares Regression Description: This model and data are an example of fitting sigmoidal growth curves taken from Ratkowsky (1983). The response variable is the dry weight of onion bulbs and tops, and the predictor variable is growing time. Reference: Ratkowsky, D.A. (1983). Nonlinear Regression Modeling. New York, NY: Marcel Dekker, pp. 62 and 88. Data: 1 Response (y = onion bulb dry weight) 1 Predictor (x = growing time) 15 Observations Higher Level of Difficulty Observed Data Model: Exponential Class 4 Parameters (b1 to b4) y = b1 / ((1+exp[b2-b3*x])**(1/b4)) + e Starting Values Certified Values Start 1 Start 2 Parameter Standard Deviation b1 = 100 700 6.9964151270E+02 1.6302297817E+01 b2 = 10 5 5.2771253025E+00 2.0828735829E+00 b3 = 1 0.75 7.5962938329E-01 1.9566123451E-01 b4 = 1 1.3 1.2792483859E+00 6.8761936385E-01 Residual Sum of Squares: 8.7864049080E+03 Residual Standard Deviation: 2.8262414662E+01 Degrees of Freedom: 9 Number of Observations: 15 Data: y x 16.08E0 1.0E0 33.83E0 2.0E0 65.80E0 3.0E0 97.20E0 4.0E0 191.55E0 5.0E0 326.20E0 6.0E0 386.87E0 7.0E0 520.53E0 8.0E0 590.03E0 9.0E0 651.92E0 10.0E0 724.93E0 11.0E0 699.56E0 12.0E0 689.96E0 13.0E0 637.56E0 14.0E0 717.41E0 15.0E0