Version info: Code for this page was tested in SAS 9.3 Zero-inflated Poisson regression is used to model count data that has an excess of zero counts. Further, theory suggests…
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Version info: Code for this page was tested in SAS 9.3. Zero-truncated negative binomial regression is used to model count data for which the value zero cannot occur and when…
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Version info: Code for this page was tested in SAS 9.3 Zero-truncated poisson regression is used to model count data for which the value zero cannot occur. Please Note: The…
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Note: This page is designed to show the how multilevel model can be done using R and to be able to compare the results with those in the book. On…
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Predictive Mean Matching (PMM) is a semi-parametric imputation approach. It is similar to the regression method except that for each missing value, it fills in a value randomly from among…
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Date variables can pose a challenge in data management. This is true in any package and different packages handle date values differently. This page aims to provide an overview of…
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The purpose of this page is to introduce estimation of standard errors using the delta method. Examples include manual calculation of standard errors via the delta method and then confirmation…
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We covered how to visualize aggregate longitudinal data here. When there are not too many unique units, it can also be helpful to view the individual growth curves. This technique…
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Importing formatted data files using the functions in the foreign package The foreign package contains functions that will allow you to import data files from some of the most commonly…
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Opening SPLUS Data Files Using the File Menu Opening SPLUS Data Files Using the openData Function Importing Formatted Data Files Using the Import Menu Importing Formatted Data files Using the…
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