Smearing retransformation

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The Smearing retransformation is used in regression analysis, after estimating the logarithm of a variable. Estimating the logarithm of a variable instead of the variable itself is a common technique to more closely approximate normality. In order to retransform the variable back to level from log, the Smearing retransformation is used.

If the log-transformed variable y is estimated as:

log(y) = f(X) + er

then, the level variable is given by:

y = exp(f(X))exp(er).