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

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: new package seqlogit available on ssc |

Date |
Thu, 16 Aug 2007 12:25:35 +0100 (BST) |

Thanks to Kit Baum a new package called -seqlogit- is now available on ssc. This package fits a sequential logit model. Traditionally, the aim of a sequential logit model is to study a process that can be described as a series of choices between a small number of options. However, these choices eventually lead to an end result. The aim of this package is to not only study the effects of explanatory variables on these choices (study the process), but also study the effects on the end result. For example, in education parents make a series of choices at what type of schools to send their children. Typically, the aim of the model is explore the effects of explanatory variables on the probabilities of continuing from one level to the next, i.e. study the process through which education is attained. However, in the end this process lead to an outcome: highest achieved level of education. Both the process and the end result are of substantive interest and are related to one another, but they are not the same. This package implements a method by Buis (2007) to study simultaneously the effect of explanatory variables on the process (the probability of passing from one level to the next) and the final outcome (highest achieved level). The effect of the explanatory variable on the end result can be shown to be a weighted sum of the log odds of passing the transitions. The weights are the product of the following three elements: o the proportion of people at risk of passing the transition, so a transition receives more weight if more people are at risk of passing it. o the variance of the dummy indicating whether the transition was passed or not, so a transition receives more weight if close to 50% pass, and less weight if virtually everybody passes or fails that transition. o the expected difference in outcome between those that pass and those that fail the transition, so a transition receives more weight if people gain more from passing it. -seqlogit- will estimate a sequential logit and allows one to use -predict- to predict the weights, and its components. Furthermore, it contains the -seqlogitdecomp- command, which graphically displays the decomposition of the effect of the explanatory variable on the end result into the effects of the explanatory variable on the individual transitions and their weights. This package also contains three ancillary files, that describe an example. The files are a do-file that implements the example, the dataset used by the do-file, and a pdf-file which shows the output and explains some of the tricks used in the example. To install the package and the ancillary files type -ssc install seqlogit, all- I will give a presentation on this package on Friday September 7 at the 2007 Nordic and Baltic Stata Users Group meeting. Note: What I call here a sequential logit model is also known under a number of different names: sequential response model (maddala 1983), continuation ratio logit (Agresti 2002), model for nested dichotomies (fox 1997), and the Mare model (shavit and blossfeld93) (after (Mare 1981)). References: Agresti, Alan 2002 . Categorical Data Analysis, 2nd edition. Hoboken, NJ: Wiley-Interscience. Buis, Maarten L. 2007 ``Not all transitions are equal: The relationship between inequality of educational opportunities and inequality of educational outcomes'' http://home.fsw.vu.nl/m.buis/wp/distmare.html. Fox, John 1997 Applied Regression Analysis, Linear Models, and Related Methods. Thousand Oaks: Sage. Maddala, G.S. 1983 Limited Dependent and Qualitative Variables in Econometrics Cambridge: Cambridge University Press. Mare, Robert D. 1981 ``Change and Stability in educational stratification'' American Sociological Review, 46(1), p.p. 72-87. Shavit, Yossi and Hans-Peter Blossfeld 1993 Persistent Inequality: Changing Educational Attainment in Thirteen Countries Boulder: Westview Press. ----------------------------------------- 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/ ----------------------------------------- ___________________________________________________________ Yahoo! Answers - Got a question? Someone out there knows the answer. Try it now. http://uk.answers.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/

**Follow-Ups**:**Re: st: new package seqlogit available on ssc***From:*"Anders Alexandersson" <andersalex@gmail.com>

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