A graph plotted from known concentrations to determine unknown sample concentrations is called what?

• A. Calibration curve
• B. Control chart
• C. Standard Curve
• D. Regression line

Answer: (C)

When you want to determine an unknown concentration, you create a standard curve. You prepare several standards with known concentrations, measure the instrument response for each, and plot that response versus concentration. This curve becomes the reference you use to read off the concentration of an unknown by finding where its response falls on the curve. The term standard curve emphasizes the use of known standards to map signal to concentration, which is why it fits best here. A calibration curve is similar but the question focuses on the standard-based approach. A regression line is just the mathematical fit through the data and may be part of the curve, but the overall graph created from known standards is the standard curve. A control chart is for monitoring a process over time, not determining concentrations.