If we know what to regress upon, what carrier to use, we would diagnose non-linearity of response by fitting a linear regression of response as c 0   +   c 1   ( a p p r o p r i a t e   c a r r i e r )   +   c 2   ( a   c u r v e d   c a r r i e r ) https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780367811846/9aebcb79-b449-46c9-a365-e81d4d6a2239/content/eq157.tif"/>