**Editor for this issue:** Brett Churchill <brettlinguistlist.org>

- Mario Cal Varela, Sum: GoldVarb

Dear fellow linguists, two weeks ago I posted a query on linguist list regarding the use of GoldVarb. I want to thank the following people for their advice and comments: Dennis R. Preston Ron Smyth Naomi Nagy Hiroko Tajika Barbara Avila-Shah For those of you, who might be interested in using GoldVarb, I'll try to summarize their points. This was the original query: >I'm right in the middle of an analysis of /t,d/ deletion in a second language variety of English using Goldvarb 2.1. I have selected the step up/step down option so I have got to the point where the program gives me a probability value for each of the factors in those factor groups that turned out to be significant. Now, in order to decide which of the factors to collapse for further runs of the program, I need to know which of the differences among the factors in each group are actually significant. But I don't know how to proceed. Could anyone out there help me with this? Thank you very much in advance. Dennis Preston warns me that the right way to proceed is to run the step up/ step down analysis first and discard the non-significant factor groups (...) >>You then go on to run VARBRUL itself (the so called-"binomial" run). When >>you get the results from this you can investigate the probability for >>"close-score" factors in individual factor groups. (A hint that there are >>such things will be large (significant) chi-square values (which you don't >>want). >> >>Of course, you can't combine close factors unless they "make sense" >>linguistically. If, for example, you find that an environment beofre /l/ >>has a.62 probability and an environment before /r/ has a .58 probability, >>then you are justified in collapsing them into a new (single) cateogry >>within that factor group, called, say, "liquids." If two scores are similar >>for low vowels and sibilants, there would be no such justification. >> >>Rememebr, you must test for significance AFTER collapse (comparing that run >>to the previous one by using the log-likelihood method described in most of >>the literature). If there is a significant difference between the two runs, >>then you must go back to the pre-collapsed run. The log-likelihood method referred to here seems to be well described in the last chapter of R. Bailey & D. Preston. 1996. Second Language Acquisition and Linguistic Variation. Benjamins. pp. 253-306. Barbara Avila kindly provided me with a short summary of the procedure: -Each VARBRUL run gives you in the output a negative number which is labeled log likelihood. For the two runs that are being compared, calculate the difference between the two log likelihoods (Just take the absolute value). -Multiply this number by two. -Figure out the difference in degrees of freedom between the two runs. The number in degrees of freedom for any run is the total number of factors in the run minus the number of factor groups. - Now look in a chi-square table. You have the number of degrees of freedom that you just calculated as the difference between the two runs, and your test statistic (chi-square value) is the doubled difference between the two log-likelihoods. If your test statistic corresponds to a P of less than .05, then the difference between the factors that you combined is significant, and combining the factors obscures a significant influence on the variation under study. Finally, Ron Smyth calls my attention to two limitations of the variable rule applications that could perhaps be commented on by more statistically-oriented researches than myself. The first one has to do with the fact that when the design has several factors, the output of the program does not give any information about some of the interactions. The other is that the program seems to handle nicely data with very few subjects per cell, where other applications would not give out anything significant. That is, GoldVarb does not keep track of subjects and seems to disregard individual differences. Mario Cal Varela Departamento de Filoloxia Inglesa e Alemana, despacho 307 Facultade de Filoloxia Universidade de Santiago de Compostela c/ Burgo das Nacions s/n Santiago 15705 ESPANA tlf (981) 563100 ext. 11858 fax (981) 574646Mail to author|Respond to list|Read more issues|LINGUIST home page|Top of issue