A.3.4—Graph intercepts

An intercept is where a fitted relationship crosses an axis. It can represent a threshold, baseline or model parameter only when the variables and units make that interpretation meaningful.

Read the axis scale carefully, distinguish measured from extrapolated intercepts and report uncertainty when the crossing is not directly observed.

A compensation point where net photosynthesis is zero can be estimated from a graph, but it should not be read beyond the measured light range without qualification.

An intercept caused by extending a line is not automatically a real zero or threshold.