In a survey people were asked, “Is addiction a disease or are addicts weak-willed?” The response was in three categories, 0 = “addicts are weak-willed,” 1 = “addiction is a disease,” or 2 = “both alternatives hold”. Use an appropriate model to examine how the response depends on respondent’s gender (0 = male, 1 = female), age, and academic status (1 = academic or 0 = otherwise). The dataset is available as addiction{catdata}.

1 load package

pacman::p_load(tidyverse, MASS, pscl)

2 Input data

data(addiction, package = "catdata")
head(addiction)
##   ill gender age university
## 1   1      1  61          0
## 2   0      1  43          0
## 3   2      0  44          0
## 4   0      1  21          1
## 5   0      0  33          0
## 6   1      0  83          0
# check data structure
str(addiction)
## 'data.frame':    712 obs. of  4 variables:
##  $ ill       : int  1 0 2 0 0 1 0 1 1 1 ...
##  $ gender    : int  1 1 0 1 0 0 0 0 1 0 ...
##  $ age       : int  61 43 44 21 33 83 29 61 37 19 ...
##  $ university: int  0 0 0 1 0 0 0 0 0 0 ...
m0_addic<-glm(ill~factor(gender)+age+factor(university), data=addiction, family = poisson)
summary(m0_addic)
## 
## Call:
## glm(formula = ill ~ factor(gender) + age + factor(university), 
##     family = poisson, data = addiction)
## 
## Deviance Residuals: 
##      Min        1Q    Median        3Q       Max  
## -1.92293  -1.17525   0.01138   0.33807   1.33959  
## 
## Coefficients:
##                      Estimate Std. Error z value Pr(>|z|)    
## (Intercept)         -0.570631   0.113507  -5.027 4.98e-07 ***
## factor(gender)1      0.081732   0.079617   1.027  0.30462    
## age                  0.010792   0.002222   4.857 1.19e-06 ***
## factor(university)1  0.235455   0.084554   2.785  0.00536 ** 
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## (Dispersion parameter for poisson family taken to be 1)
## 
##     Null deviance: 528.42  on 681  degrees of freedom
## Residual deviance: 498.77  on 678  degrees of freedom
##   (30 observations deleted due to missingness)
## AIC: 1570.6
## 
## Number of Fisher Scoring iterations: 5

3 The end