Statistical model for transgene copy number determination with external standard curve method. A. The simple linear regression model with LDNA (logarithm transformed input DNA amount) as dependent variable, and Ct number as independent variable. The external standard curve can be used for calculating input DNA amount from transgenic and control samples. The regression slope can be used for data quality control to estimate amplification efficiency. B. The linear regression as shown by plot of logarithm 2 based transformation of initial DNA input against Ct number.