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Table 1 Comparison of five S-shaped models to fit the PCR curve: Sigmoid, Richards, Gompertz, Hill and Chapman.

From: A new real-time PCR method to overcome significant quantitative inaccuracy due to slight amplification inhibition

Name

Equation

Estimated Parameters

R 2

Adj R 2

Standard Error of Estimate

  

F max

b

c

F b

d

   

Sigmoid

f = F b +F max /(1+exp(-(x-c)/b))

45.11

1.49

22.37

-0.03

 

1

1

0.1354

Richards

f = F b +(F max /(1+exp(-(1/b)*(x-c)))^d)

45.11

1.58

21.95

0.02

1.20

1

1

0.0926

Gompertz

f = F b +F max *exp(-exp(-(x-c)/b))

45.19

2.15

21.45

 

0.29

0.9992

0.9992

0.6006

Hill

f = F b +F max *x^b/(d^b+x^b)

45.18

14.95

 

0.08

22.34

1

1

0.1351

Chapman

f = F b +F max *(1-exp(-b*x))^d

45.19

0.46

 

0.29

20615

0.9992

0.9992

0.6006

  1. In this table, f is the fluorescence at cycle x; F max represents the maximum fluorescence value; F b is the background reaction fluorescence; b, c and d determine the shape of each curve. For each model the determination coefficient (R2), the adjusted determination coefficient (Adj R2) and the standard error of estimate have been calculated.