how to interpret the summary of a glm poisson

Question

I need a little help with the interpretation of my model's summary.

First, here is the model :

glm(formula = Nb_bone_discovery ~ Order * Time, family = "quasipoisson") #I used quasipoisson since I got surdispersion.

Where :

Order is a discret variable with 3 modalities ["Carnivora","Human","Marsupial"]
Nb_bone_discovery is a discrete quantitative variables. ex: ["0,1,2..."]
Time is a Continuous quantitative variables ex: ["0.33,0.5,0.8,1,2..."]

To be more precise I try with this model to show that the Order factor will have an effect on the number of bone_discoveries, while removing the effect of Time, since theoretically, the more time passes, the greater the number of bone discoveries is anyway.

SO here is the results:

Deviance Residuals: 
    Min       1Q   Median       3Q      Max  
-2.5270  -1.2207  -0.5733   0.6993   2.7131  

Coefficients:
                 Estimate   Std. Error  t value   Pr(>|t|)    
(Intercept)      -0.5916    0.1794      -3.297    0.001148 ** 
Human            1.0946     0.2379       4.600    7.31e-06 ***
Marsupial        0.6850     0.3005       2.280    0.023632 *  
Time             12.1964    3.2483       3.755    0.000225 ***
Human:Time       -11.3398   3.6346       -3.120   0.002064 ** 
Marsupial:Time   -9.0848    4.3548       -2.086   0.038179 *

Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

(Dispersion parameter for quasipoisson family taken to be 1.446357)

    Null deviance: 388.61  on 214  degrees of freedom
Residual deviance: 339.54  on 209  degrees of freedom
  (32 observations deleted due to missingness)
AIC: NA

Number of Fisher Scoring iterations: 5

With that summary is it correct to say the following things :

Having an Human Order predisposes to more discovered bones (if you are Human you have 1.0946 more bones discovered than if you are Carnivora)
Being Human almost eliminates the Time effect (12.1964 -11.3398 =~0.85: you gain 0.85 bones discoveries per unit of Time when you are Human)
Being Marsupial does not decrease the Time effect as much (12.1964-9.0848 =~3.11 : you gain 3.11 bones discoveries per unit of Time when you are Marsupial)

I'm correct, and did I miss some other interpretations from that summary ?

Can I say that overall, bones are more discovered in Human order compared to the others?

Thanks a lot for your help

how to interpret the summary of a glm poisson

0 Answers0