Let's assume we have a normal distribution X∼N(μ,σ2). In a normal distribution the quantile can be calculated as follows:
Φ−1X(p)=μ+σ√2erf−1(2p−1)
If we want to calculate the value in the future of a stock we map it as:
Y=exp(X)
I would like to know that if the function of the quantile can be calculated based directly on:
Φ−1Y(p)=exp(μ−σ/2+σ√2erf−1(2p−1))
The part of the equation −σ/2 is extracted from îto calculus, however, I cannot find anywhere the correctness of this equation (I deduced it). I think the function exp is monotonic, so, it should preserve the value for the quantiles, but I'm not certain. One of my certainties is that μ changed to μ−σ/2, I have no idea if that modifies in some way the calculation of Φ−1Y(p), or if σ also changed.
Answer
Quantiles are preserved under monotonic transformations, hence the quantile for Y is simply the exponential of the quantile of X, no need for corrections whatsoever (see here for instance).
Put otherwise, let q denote the quantile α of X i.e. P(X≤q)=α
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