# glm

1. ### Generalized Linear Model and fixed effects

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)...
2. ### Dispersion parameter

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+...
3. ### How to best combine 3 repeated experiments

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...
4. ### Which kind of general linear model?

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...
5. ### problems with Analysis Of Variance of unbalanced non parametric data

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...
6. ### SPSS v21 - MANCOVA post-hoc test - post-hoc box grayed out

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...
7. ### Which statistical test? GEE?

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...
8. ### Statictical suggestion regarding DOE and GLM for the pharmacutical related problem

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...
10. ### Problems with S+ and nested GLM models

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...
11. ### Can an explanatory variable be both a random and fixed effect simultaneously?

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...
12. ### Nested test to remedy pseudoreplication

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...
13. ### GLM with Linear Dependencies

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...
14. ### GLM with Random Factors

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...
15. ### GLM questions for landscape experiment

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...
16. ### What is a link function (in English)

In generalized linear models there are link functions. I would like if someone could explain the concept to me. Thanks!
17. ### How to predict a model with multiple factors?

Hi, My question is probably trivial but I cannot figure it out... I'm doing a glm with multiple continuous and categorical predictors. In R, the summary() gives the estimates of factors' levels as contrast to the intercept (right?). So, If I'm modelling, let's say, diet and sociality as...
18. ### Logistic regression or GLM?

Hi everyone: I have a question about using logistic regression or GLM with only categorical variables as independent variables. The dependent variable y is shown as binary coded data where 1=males and 0=females. Each corresponding to an excrement. The independent variables are as follows...
19. ### Variation in inflection point for modeled logistic curve

Hey all. Question category: R and regression; Posted in R forum since R code. Question: How best to quantify variation in an inflection point for a logistic curve? Background of problem: Birdies begin their birdie lives contained in eggs. Then, they hatch and continue their lives...
20. ### Regression Analysis - Transformations and Non-Normality

Hello, I am fairly new to regression analysis and have a few questions.. I have a fairly large dataset containing information about 144 municipalities in a country. I am trying to create a model that uses a number of independent variables (urban ratio, literacy rate etc.) to model the...