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From |
jaswartz <jaswartz@uic.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Question about large data set analyses and survey logistic regressions |

Date |
Sun, 4 Jan 2004 14:42:57 -0600 |

All, I am new to the list and relatively new to Stata. I hope my questions have not been addressed too much before but, if so, I would appreciate being pointed in the direction of the archives. I have done some snooping on my own but have not found anything that addresses my specific issues. Here they are: I am analyzing data collected as part of the National Household Survey on Drug Abuse. The data set contains about 39,000 observations. I am using weights provided by RTI, which conducts the survey, to obtain accurate point and standard error estimates. Hence, I am using the svylogistic procedure in Stata to incorporate these weights. Before running my logistic regressions, I ran some bivariate stats using svytab. Because of the large sample size, everything comes out statistically significant looking at the Chi-Square results for the bivariate statistics. My first question is: Is there a way to run bivariate statistics on a large data set like this to find non-trivial, significant relationships. For instance, could I draw a random sample of size N from my complete sample, to obtain statistical power of about .80 and run the bivariates on that random sample? Or, is there a more preferred way of analyzing these data? My second question is with the svylogistic regression procedures. The output does not give you a pseudo-R square as the regular logistic regression procedure does. Is there a way to get an effect size estimate using the svylogistic procedure or should I just run the logistic procedure and use that estimate? Finally, all of my model fit statistics seem to come up significant with this data set meaning my models are not fitting the data well. Is this also attributable to the large data set size? Is there a preferred way of conducting model diagnostics when the data set is this large? You can respond directly to my email at jaswartz@uic.edu. Thanks very much for any help. James * * 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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