glm

Hello everyone! :wave: I'm having some trouble resolving two assignments with SPSS. First one is that I need to analyse if there's a difference between poor and rich European countries (using a GDP per capita index variable) and link it with thinking that the environment is the most important...

Hello all, I'm attempting to fit a model where y variable is a variety of $/ha/year figures (all positive) ranging between 0.01 and 2520. The output of this should always have positive fitted values (none of these values should ever be below 0), and yet I get constant negative fitted values...

When using a GLM or GLMM with a negative binomial distribution in R it is usually necessary to set the value of theta in the model. But what does theta actually stand for? And how do I caluclate it? I have been able to get around this for now by setting my models to calculate theta for me...

I am investigating the factors that influence the bycatch of dolphins using a poisson GLM. My response variable is bycatch rate per unit effort and varies from 0 to 0.125. However, my response is very zero-inflated (2304 of 2436 observations are zero). I have three response variables (two...

I want to estimate a model with a fractional outcome variable following Papke & Wooldridge (2002). I run glm dep_var independent_var, family(binomial) link(logit) robust, right? How can I add a three level fixed effects? My approach until now was to use egen new_var = group(var1 var2 var3)...

I have the understanding that the dispersion parameter, \phi, in generalised linear models needs to be known for deviance to meaningful or otherwise it can be estimated from the model, but no analysis of deviance can be carried out. Why is it then that in binomial and poisson models in R/S+...

Hi there, I would appreciate some expert advice on how to best combine 3 replicated experiments into one analysis. I’m trying to check if a treatment effects growth of a plant Lemna minor. I have a highly controlled environment, but because of a space limitations were only able to use 3...

Hello statisticians, Let me introduce myself. I am a 19 year old student Applied Economic Sciences at the University of Antwerp (Belgium). We are given a task for the course 'regression and anova' consisting of 5 questions. The first four questions were no problem but I'm stuck at the last...

Hello fellow R users :wave: I hope someone can help me solve this problem. I've been looking for a solution all day. I have a proportional response (% cover) variable. I have 2 explanatory factors, both with 3 or more levels: quadrats (of which there are many) and year (of which there are...

Hi everyone, I'm looking to run a Tukey post-hoc test in GLM-->Multivariate with covariates (MANCOVA). When I add covariates I can no longer select "post-hoc" - the box is grayed out. Also, I can't click "compare main effects" in the options tab. Why is this? I have seen a thread...

Hello! I'm currently playing which my data and am unsure about the statistical test to use. I have MRI data from 25 patients. I have 4 (predetermined) lesion types and a control area from which I obtained MRI values. Not all patients have all lesion types, some patients have several of the...

We performed a DOE to study the relationship between simulated intestinal fluid (SIF) components and solubility of drugs. The DOE is composed of 7 factors (representing the components of SIF) and 2 levels for each drug. And we have done several drugs with the DOE. Now with the DOE analysis, we...

hi everyone! I have the following question: while running univariate GLM, I have encountered the situation when mean differences between groups are the same, but in one test they reach statistical significance, whereas in other not. Probably the reason is that in one case std. deviations are...

Hi I was wondering if someone might be able to help. My department has just changed statistic programs to S+ and I'm trying to run a multi-factorial GLM with one nested factor (design below). What was simple task in our old software has stumped everyone in my department. Does anyone know how...

Hello, and thank you for reading. I am trying to test for what environmental variables (3 continuous distance variables e.g. distance from nearest village) influence 1) species richness at the site level (continuous variable) and 2) community composition at the site level (coordinates of...

Hello and thanks for taking the time to read this. Data structure: I have two datasets from two protected areas that differ in protection status. Both areas contain 43 and 37 sites each. Question: I would like to know which test would be the best for testing whether the PA status has...

Hi: Newbie to SPSS. Tons of stats and programming knowledge ... but helping a novice with their SPSS work. If I was doing this as a regression in package where I had to type in my own variables, this wouldn't be an issue. I have 2 fixed factors, A and B. There 3 values of A. B is a...

Hi: Newbie to SPSS. Tons of stats and programming knowledge ... but helping a novice with their SPSS work. We're doing a GLM with a random factor. When I put a factor in (incorrectly) as fixed I get one less piece of output, and when I put the factor in (correctly) as random I'd like to...

I am analyzing bird count data from surveys conducted each week (from Nov-April, when bird foraging most active near breeding cycle) for 6 years in 9 large experimental plots that are split amongst 3 regions in the landscape (6 yrs x 3 regions x 3 plots/region). We are interested in comparing...

In generalized linear models there are link functions. I would like if someone could explain the concept to me. Thanks!