Four-parameter logistic (4-PL) curve

An S-shaped curve model used for immunoassay standard curves, defined by a lower plateau, an upper plateau, a mid-point concentration and a slope factor. The five-parameter version (5-PL) adds a term for asymmetry.

• Also: 4-PL
• Also: 4PL
• Also: 5-PL
• Also: five-parameter logistic
• Also: sigmoidal curve fit