glm

  1. H

    Transform data for factorial two-way ANOVA/General Linear Model??

    Hi, I'm not very statistically minded but I would really appreciate some guidance. I am needing to do several stat tests for my MSc dissertation. I have one dependent variable (species count) and one independent variable (year), but two species. I have constructed a basic count against year...
  2. H

    Repeated measures design - correct analyses and GLM assumptions

    Hi all, I have collected data for a study but I am not sure now if I am carrying out the correct analyses. I have tried for the last few days to figure out whether my analyses are correct, but I keep getting a lingering doubt that they are not and so I thought I will ask this question because...
  3. O

    Indices with data bound between -1 and +1

    Hi all, I would really appreciate some advice on how to deal with my data. I would like to compare data calculated from an index which is bounded by -1 and +1. I was surprised to see that previously published use of this index has been analysed using standard ANOVA, because I was led to...
  4. E

    Help with glm--- Simple Logistic Regression

    Hi All! Thanks for reading. I wanted to compare month of sample collection (April, May, June, and July) to presence/absence data (coded in binary dummy variables). I tried to run a Simple logistic regression, but realized that the output table with p values, etc all report for may, June, and...
  5. I

    GLM in SPSS

    Hi, I am trying to do something quite simple but I am so confused about how to enter my data into SPSS and which test to use. I have four subjects whose performance is measured at ten time points and I want to know if their scores are changing. Normally I would enter my data with one subject...
  6. A

    Fixed term is “(Intercept)” --Dredge function

    Hi, i'm currently running a glm model in R and have attempted to use the following code: Model: resultsnew<-glm(R0A1~MP_Perc+MPHW_Perc+HW_Perc+YP_Perc+AG_Perc+Shrub_Perc+Dist_CountyRoad+Dist_PrimaryRoad+Dist_SecondaryRoad+Dist_TertFireRoad,data=secondorder,family=binomial("logit"))...
  7. T

    Help with model Matrix GLM

    Hey guys been browsing the forums for a while, and usually find what I need! This is a tad more specific though so Ive made an account!! I've been puzzled by the form of the model for a while.. The model states that the response depends upon y~smoke + drink +smoke:drink +age:smoke. The model...
  8. A

    Binomial response variable with 3 continuous and 1 categorical predictor. Best test?

    Hello I have a binomial response variable. Predictors are composed of 3 continuous variables (the results of a Principle Components Analysis of habitat structure variables) and 1 categorical variable (habitat type e.g. grazed or ungrazed). I want to test whether the 3 habitat variables have...
  9. B

    Type I and Type II SS for ANOVA, non-statistician

    Good Afternoon (non-statistician here), I have to automate a GLM within an Excel sheet that will be analyzing some toxicity data, resulted from scoring cell aberrations. And, I'm using MiniTab to validate the estimates. MiniTab is using Type I (sequential) SS and Type II (adjusted) SS within...
  10. J

    How to model weighted average ratios in the [0,1] interval

    Maarten Buis on this forum provided great insight on how to model percentages in the [0,1] interval (http://www.talkstats.com/showthread.php/52986-Modelling-percentages-in-the-closed-interval-0-1). I now have a similar but somewhat different problem, in that I'd need to model weighted average...
  11. J

    Maximum likelihood estimation and GLMs - can you help me refresh my rusty memory?

    Hi all, I was wondering if you can help me refresh my rusty memory on maximum likelihood estimation. I think I remember the basic concept from my university courses in a previous life. Banal example: we want to fit a normal distribution to the observations 3,4,5, then N(4,1) is the best...
  12. R

    Data analysis with a GEE, is my method valid?

    Hi everyone, I’ve been doing some statistical analyses in R on some data. It’s for use in a manuscript I’m hoping to get published in a biological journal. Unfortunately, the tests I ended up having to run are kind of at the limit of my understanding, so I was hoping that I could run through...
  13. M

    GLM with non-parametric post hoc testing?

    Hi guys, I have a question regarding the appropriate use of comparisons for independent samples (3 factor levels), please. Overall sample size is N=546, subsamples: 218 or 228 or 100), convenience sampling, stratified. I use ANOVA with post hoc Tukey, if Levene indicates variance...
  14. H

    Comparing count data and cultivars in R

    Hi, I'm trying to analyse an experiment with this setup: A plant species with 16 different cultivars of 4-5 plants per cultivar (completely randomised within greenhouse, no blocks) An insect species that was allowed to spread freely for 4 days on the plants. The insect number per plant was...
  15. H

    How to analyse deviance (GLM in R)

    Hi! This might be quite basic, but how do I analyse the fit of my GLM from the deviance? In the summary of my model, I get a deviance of 140.1 (df.resid = 52). Can I tell from these numbers, if the fit is acceptable? Thanks in advance for any replies!:tup:
  16. H

    Fit of generalized linear model (Poisson distribution)

    Hi guys Can anyone tell us how to evaluate the fit of our generalized linear model with a poisson distribution? We can't really tell if the model is a good fit or not. Do you use the deviance to answer this question? If so, what does it tell us in the following example? Thank you in advance...
  17. W

    Which statistical analyses do I need to use?

    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...
  18. S

    Constant negative fitted values...am I missing something?

    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...
  19. S

    In a negative binomial GLM or GLMM what does theta stand for?

    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...
  20. P

    Bycatch of dolphins data, zero inflated and under-dispersed - what next?

    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...