In biology often it is of interest to describe life span of an organism. Parametric approach to this problem involves fitting a given probability distribution. Common distributions used here are exponential, Weibul and Gamma. Occasionally other distributions such as inverse Gaussian, log-normal distribution etc. are also fitted. The data refer to age at death of a species of sheep. Age was estimated using skulls. In case of the above data usual distributions failed to give a good fit. There is considerable improvement by using, instead, a quadratic hazard function.
A data frame with 11 observations on the following 2 variables.
Age at death (years)
Estimate parameters by maximum likelihood and test goodness of fit using chi-square test.