X-Nico

Median absolute deviation

The factor $1.4826\backslash \; \backslash approx\; 1/\backslash left(\backslash Phi^\{-1\}(3/4)\backslash right)$ results from the reciprocal of the normal inverse cumulative distribution function, $\backslash Phi^\{-1\}(P)$, evaluated at probability $P=3/4$.

Strictly standardized mean difference

In a primary screen without replicates, assuming the measured value (usually on the log scale) in a well for a tested compound is $X\; i$ and the negative reference in that plate has sample size $n\; N$, sample mean $\backslash bar\{X\}\; N$, median $\backslash tilde\{X\}\; N$, standard deviation $s\; N$ and median absolute deviation $\backslash tilde\{s\}\; N$, the SSMD for this compound is estimated as

see also