1 NIST/ITL StRD 2 Dataset Name: Rat43 (Rat43.dat) 3 4 File Format: ASCII 5 Starting Values (lines 41 to 44) 6 Certified Values (lines 41 to 49) 7 Data (lines 61 to 75) 8 9 Procedure: Nonlinear Least Squares Regression 10 11 Description: This model and data are an example of fitting 12 sigmoidal growth curves taken from Ratkowsky (1983). 13 The response variable is the dry weight of onion bulbs 14 and tops, and the predictor variable is growing time. 15 16 17 Reference: Ratkowsky, D.A. (1983). 18 Nonlinear Regression Modeling. 19 New York, NY: Marcel Dekker, pp. 62 and 88. 20 21 22 23 24 25 Data: 1 Response (y = onion bulb dry weight) 26 1 Predictor (x = growing time) 27 15 Observations 28 Higher Level of Difficulty 29 Observed Data 30 31 Model: Exponential Class 32 4 Parameters (b1 to b4) 33 34 y = b1 / ((1+exp[b2-b3*x])**(1/b4)) + e 35 36 37 38 Starting Values Certified Values 39 40 Start 1 Start 2 Parameter Standard Deviation 41 b1 = 100 700 6.9964151270E+02 1.6302297817E+01 42 b2 = 10 5 5.2771253025E+00 2.0828735829E+00 43 b3 = 1 0.75 7.5962938329E-01 1.9566123451E-01 44 b4 = 1 1.3 1.2792483859E+00 6.8761936385E-01 45 46 Residual Sum of Squares: 8.7864049080E+03 47 Residual Standard Deviation: 2.8262414662E+01 48 Degrees of Freedom: 9 49 Number of Observations: 15 50 51 52 53 54 55 56 57 58 59 60 Data: y x 61 16.08E0 1.0E0 62 33.83E0 2.0E0 63 65.80E0 3.0E0 64 97.20E0 4.0E0 65 191.55E0 5.0E0 66 326.20E0 6.0E0 67 386.87E0 7.0E0 68 520.53E0 8.0E0 69 590.03E0 9.0E0 70 651.92E0 10.0E0 71 724.93E0 11.0E0 72 699.56E0 12.0E0 73 689.96E0 13.0E0 74 637.56E0 14.0E0 75 717.41E0 15.0E0 76
