What is the primary purpose of generating a standard curve in experimental design?

A standard curve is made by measuring the response of a detector to a series of samples with known concentrations. By plotting those concentrations against the measured signals, you create a reference line that shows how signal changes with amount. This line lets you read off the concentration of an unknown sample by finding where its signal falls on the curve. It also checks that the instrument is working correctly and that the assay is linear over the range used. For example, in a Bradford protein assay, you would plot absorbance for known protein amounts; then you can calculate the protein level in a test sample by locating its absorbance on that curve.