Talk:Cornish–Fisher expansion

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Redundancy in notation for cumulant

The second cumulant is variance. However, both symbols σ^2 and κ_2 are used in the article. par (talk) 18:00, 8 March 2017 (UTC)[reply]

Percentile of the standard normal

Article says "Let z be a normally distributed random variable and let z_α be the value of z at the αth percentile. As an illustration of this last definition when α = 0.95, z_α = 1.96." Shouldn't this be α = 0.975, zα = 1.96, the correct percentile of the standard normal distribution?141.160.5.251 (talk) 19:14, 28 April 2014 (UTC)[reply]

The notation for normal quantiles varies. Sometimes they are indexed by the confidence interval probability (as the article currently does), other times by the left cumulative probability (as you did), and still others by the right cumulative probability. I'll change the text to your notation, since it's the one used on the page on the normal distribution and, more importantly, according to a few external sources I consulted it's the one use in the formula of the Cornish-Fisher expansion. FilipeS (talk) 11:34, 23 July 2014 (UTC)[reply]