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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
stata list <statalist@hsphsun2.harvard.edu> |

Subject |
st: update hangroot |

Date |
Fri, 30 Nov 2007 17:58:25 +0000 (GMT) |

Thanks to Kit an update of the -hangroot- package is now available from -ssc-. This update adds two new features: the possibility to add confidence intervals and new distributions. To update type -ssc install hangroot, replace- or -adoupdate, update-. -hangroot- creates a hanging rootogram (Tukey 1977, Wainer 1974), which compares a theoretical distribution with an empirical one, by "hanging" the histogram from the theoretical distribution, instead of "standing" the histogram on the x-axis. This way deviations are shown as deviations from a horizontal line (y=0) instead of deviations from a curve (the density curve). This makes it easier to spot patterns in the deviations. Also the y-axis is scaled as the square root of the frequency instead of the frequency to show deviations in the tails more clearly. To quote one happy user: "-hangroot- is really fun to play with". This update adds the possibility to add confidence intervals around the bottom of the bars. These confidence intervals assume that the number of observations in a bin follow a multinomial distribution, and use Goodman's (1965) approximation of the simultaneous confidence interval. These confidence intervals do not take into account that the parameters in the theoretical distribution are also estimated. Also, these confidence intervals do not take into account that nearby bins are likely to be similar, as was suggested by Vermeesch (2005). However, I would consider this latter point a feature, as this corresponds with the simple non-parametric logic that is behind the histogram and the (hanging) rootogram. This update also increases the number of theoretical distributions supported. Apart from the normal (Gaussian), beta, Pareto, and Poisson distribution that were already implemented, -hangroot- now also supports the exponential, Laplace, uniform, and geometric distributions. Two example datasets are available. One file records the number of deaths due to being kicked by horses in 14 Prussian cavalry units between 1875 and 1894, as collected Bortkiewicz (1898). This closely follows a poisson distribution. The second file records the proportions of Dutch city budgets spend on different categories 2005. These are not to far from a beta distribution. Use the -net get- command to get those files. -- Maarten References Bortkiewicz, L. (1898): Das Gesetz der kleinen Zahlen. Teubner, Leipzig. Goodman, Leo A. (1965), "On Simultaneous Confidence Intervals for Multinomial Proportions". Technometrics, 7(2), pp. 247-254. Tukey, John W. (1977), "Exploratory Data Analysis", Addison-Wesley. Vermeesch, Pieter, (2005), Statistical uncertainty associated with histograms in the Earth Sciences, Journal of Geophysical Research - Solid Earth, Vol 110, B02211. Wainer, Howard. (1974), "The Suspended Rootogram and Other Visual Displays: An Empirical Validation". The American Statistician, 28(4), pp. 143-145. ----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands visiting address: Buitenveldertselaan 3 (Metropolitan), room Z434 +31 20 5986715 http://home.fsw.vu.nl/m.buis/ ----------------------------------------- __________________________________________________________ Sent from Yahoo! - the World's favourite mail http://uk.mail.yahoo.com * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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