# Total Deviation Index

Reading Notes: Total deviation index for measuring individual agreement with applications in laboratory performance and bioequivalence TDI describes a boundary which covers the majority of the observed differences (percentage for the log transformed data)
Method Random variables Y and X
Assume finite 1st and 2nd moments with mean $\mu _y ,~ \mu _x$ , variances $\sigma _{y} ^2 ~, \sigma _{x} ^2$ and covariance $\sigma _{y,x}$
D = Y - X