I am doing some analyses on unethical behaviour scales (e.g. abuse of information) in teams of organisations. I want to analyse whether culture (perceptions of and shared culture) have an impact on unethical behaviour. I have a relatively large dataset. For example for this analysis about 3650 respondents were included in the analysis. I have data on 23 organisations and 2170 teams.

Because intra-class correlations (ICC) were low at the organisational level (below 5%), I only looked at team-level. The linear model was not appropriate because of non-normal error distribution. In a first step, I did some single level analyses on the data just for exploration. I found that, because of some overdispersion in the data, a negative binomial regression seemed better than a poisson. However, when fitting a multilevel model I had convergence problems for the negative binomial (even for the null-model) because the hessian matrix was not positive definite, but had no problem fitting the multilevel poisson regression. I was wondering whether the overdispersion in the single-level analysis may have been caused by the hierarchical structure, and that I have good reason to choose for the multilevel poisson regression. Because the null model had convergence problems for the negative binomial, and not for the poisson, maybe in a multilevel context the poisson is more appropriate? Would using a multilevel poisson regression with robust variance estimator be a valid technique for analyzing the data (this deals with the overdispersion to some extent?)? I was also wondering whether it is possible to test for overdispersion in SPSS in the multilevel context.

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    $\begingroup$ I've tagged this post analysis since it concerns the analysis of a particular dataset. So far the description is okay. However, you must include more information such as measures collected, numbers of observations, and specific aims. Please view the wiki and apply edits before we can make appropriate recommendations. stats.stackexchange.com/tags/analysis/info $\endgroup$ – AdamO Aug 18 '15 at 17:01

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