The mixed gamma ageing model in life data analysis

Parametric and non-parametric lifetime data analyses in practical applications require sensitive tools if non-monotonic ageing properties (trend changes) are to be examined. The well known bathtub-shaped hazard rate is a special model for describing a trend change in ageing properties over time. The identification of trend changes in the hazard rate can be supported by graphical tools. This paper discusses the combined application of graphical tools and parametric estimation in the flexible mixed gamma distribution family to identify trend changes and model bathtub-shaped hazard rates.     

Graphical tools for life time data analysis

It is purpose of this paper to introduce and describe graphical tools and techniques for (technically oriented) life time data analysis. The aim of this analysis is the determination of a representative statistical parametric or non-parametric model reflecting ageing behaviour over time. The paper intends to demonstrate that a subjective data analysis by graphs can be more sensitive and informative than pure parameter estimation in a predefined model or application of test statistics. In this sense some of those graphical tools are discussed which provide a less formal goodness-of-fit approach analysing the adherence to or deviation from a hypothesized distribution shape in a graph. Various graphical tools will be described and compared concerning their specific advantages and restrictions for life time data analysis. Finally some examples will demonstrate a “combined graphical analysis approach”.     

Trends in American family size diversity

Population Research and Policy Review - How diverse is American society and are Americans becoming more or less diverse? Contemporary discussions claim high and increasing diversity, but analyze...