LOGNORM.INV (p, μ, σ) = the inverse of LOGNORM.DIST( x, μ, σ, TRUE) LOGNORM.DIST( x, μ, σ, cum) = the log-normal cumulative distribution function with mean μ and standard deviation σ at x if cum = TRUE and the probability density function of the log-normal distribution if cum = FALSE. If you have data that is skewed to the right that fits the log-normal distribution, you may be able to access various tests described elsewhere in this website that require data to be normally distributed.Įxcel Functions: Excel provides the following two functions: Note that the log-normal distribution is not symmetric, but is skewed to the right.
25.įigure 1 – Chart of Log-normal Distribution In particular, since the normal distribution has very desirable properties, transforming a random variable into a variable that is normally distributed by taking the natural log can be useful.įigure 1 shows a chart of the log-normal distribution with mean 0 and standard deviations 1. Observation: As described in Transformations, sometimes it is useful to use a transformation of the population being studied. Observation: Some key statistical properties are: The probability density function (pdf) of the log-normal distribution is See Exponentials and Logs and Built-in Excel Functions for a description of the natural log.
Definition 1: A random variable x is log-normally distributed provided the natural log of x, ln x, is normally distributed.
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