S-shaped Response Model - Response Function

S-shape response function exhibits increasing returns to scale at low levels (threshold) and diminishing returns at high levels (saturation) of marketing effort

Concave and S-curve response functions

Response Curve: Measuring Diminishing Returns in Marketing, Richie Singh

Sigmoid function - Wikipedia

Advertising response curves: What are they and why do you need them?

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Functional response - Wikipedia

An S-shaped response curves representing tumor control probability

An Introduction to Impulse Response Analysis of VAR Models · r-econometrics

6 Item Response Theory Using R for Social Work Research