In Sec. 2.2, instrument calibration and the establishment of standard curves for assay methods are outlined. In Sec. 2.3 we provide a brief review of simple linear regression analysis, which is often employed in assay development. Statistical methods for determination (estimation) of an unknown sample based on an established standard curve are described in Sec. 2.4. Weight and model selections for establishing standard curves in the calibration of an instrument are discussed in Sec. 2.5. Some statistical considerations in assay development are provided in Sec. 2.6.