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Physical Sciences and Mathematics Commons

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Statistical Methodology

Todd Christopher Headrick

Non-normality

Publication Year

Articles 1 - 2 of 2

Full-Text Articles in Physical Sciences and Mathematics

A Method For Simulating Multivariate Non-Normal Distributions With Specified Standarized Cumulants And Intraclass Correlation Coefficients, Todd C. Headrick, Bruno D. Zumbo Jan 2008

A Method For Simulating Multivariate Non-Normal Distributions With Specified Standarized Cumulants And Intraclass Correlation Coefficients, Todd C. Headrick, Bruno D. Zumbo

Todd Christopher Headrick

Intraclass correlation coefficients (ICCs) are commonly used indices in subject areas such as biometrics, longitudinal data analysis, measurement theory, quality control, and survey research. The properties of the ICCs most often used are derived under the assumption of normality. However, real-world data often violate the normality assumption. In view of this, a computationally efficient procedure is developed for simulating multivariate non normal continuous distributions with specified (a) standardized cumulants, (b) Pearson intercorrelations, and (c) ICCs. The linear model specified is a two-factor design with either fixed or random effects. A numerical example is worked and the results of a Monte …


The Power Method Transformation: Its Probability Density Function, Distribution Function, And Its Further Use For Fitting Data, Todd C. Headrick, Rhonda K. Kowalchuk Mar 2007

The Power Method Transformation: Its Probability Density Function, Distribution Function, And Its Further Use For Fitting Data, Todd C. Headrick, Rhonda K. Kowalchuk

Todd Christopher Headrick

The power method polynomial transformation is a popular algorithm used for simulating non-normal distributions because of its simplicity and ease of execution. The primary limitations of the power method transformation are that its probability density function (pdf) and cumulative distribution function (cdf) are unknown. In view of this, the power method’s pdf and cdf are derived in general form. More specific properties are also derived for determining if a given transformation will also have an associated pdf in the context of polynomials of order three and five. Numerical examples and parametric plots of power method densities are provided to confirm …