Homework5

Initial set-up

# List of packages
packages <- c("tidyverse", "infer", "fst", "modelsummary", "effects", "survey", "MASS", "aod", "interactions", "kableExtra", "flextable", "scales") # add any you need here

# Install packages if they aren't installed already
new_packages <- packages[!(packages %in% installed.packages()[,"Package"])]
if(length(new_packages)) install.packages(new_packages)

# Load the packages
lapply(packages, library, character.only = TRUE)

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Homework 5 (5%): due by next lecture on March 26th

Instructions: Start a new R markdown for the homework and call it “Yourlastname_Firstname_Homework_5”.

Copy everything below from Task 1 to Task 5. Keep the task prompt and questions, and provide your code and answer underneath.

Remember: you need all the steps for your code to work, including loading your data – otherwise it will not knit.

To generate a new code box, click on the +C sign above. Underneath your code, provide your answer to the task question.

When you are done, click on “Knit” above, then “Knit to Html”. Wait for everything to compile. If you get an error like “Execution halted”, it means there are issues with your code you must fix. When all issues are fixed, it will prompt a new window. Then click on “Publish” in the top right, and then Rpubs (the first option) and follow the instructions to create your Rpubs account and get your Rpubs link for your document (i.e., html link as I provide for the tutorial).

Note: Make sure to provide both your markdown file and R pubs link. If you do not submit both, you will be penalized 2 pts. out of the 5 pts. total.

Task 1

Use data for Germany and the variable coding for model3 and model4 from the tutorial (i.e., both for the cleaning & recode, as well as the linear model formulas). Do a summary table displaying both model outputs. Interpret the coefficients for the MLR without the interaction (i.e., the first displayed model), and interpret model fit metrics for both models.

germany_data <- read_fst("germany_data.fst")

df <- germany_data

Note: you have both df and france_data which contain the french data (same observations, under different names). So you can always revert back to france_data if needed

Survey weights

From ess website:

For data collection the ess uses strictly probability-based samples. Every element in the ess target population should therefore have a greater than zero probability of being included into the sample. When analysing ess data estimates, the likelihood of each respondent to be part of the sample should also be taken into account - which means that the most accurate estimates will be obtained only after weighting the data.

Link: https://www.europeansocialsurvey.org/methodology/ess-methodology/data-processing-and-archiving/weighting

df$weight <- df$dweight * df$pweight
survey_design <- svydesign(ids = ~1, data = df, weights = ~weight)

Multiple linear regression

We will work with our populist attitudes scale based on Norris and Inglehart’s conceptualization and measurement again. So let’s run our code:

Setting up our populist scale

# Setting values greater than 10 to NA
df$trstplt <- ifelse(df$trstplt > 10, NA, df$trstplt)
df$trstprl <- ifelse(df$trstprl > 10, NA, df$trstprl)
df$trstprt <- ifelse(df$trstprt > 10, NA, df$trstprt)

# Creating and rescaling the trust variable
df$trust <- scales::rescale(df$trstplt + df$trstprl + df$trstprt, na.rm = TRUE, to = c(0, 100))

# Here's how you would "flip it" because populist is conceived by N + I as 'anti-trust'
# As Schafer explains there are some issues with that conceptualization, but N + I is also widely applied
df$populist <- scales::rescale(df$trust, na.rm = TRUE, to=c(100,0))

Now, let’s suppose we read literature about the importance of social capital, political interest, and generational trends for understanding populism.

Let’s recode the variables and see if that is supported.

df <- df %>%
  mutate(
    cohort = ifelse(yrbrn < 1930 | yrbrn > 2000, NA, yrbrn),
    # Recoding generational cohorts based on the year of birth (yrbrn).
    # The year of birth is categorized into different generational cohorts.
    # Interwar (1900-1945), Baby Boomers (1946-1964), Gen X (1965-1979), Millennials (1980-1996).
    # The 'TRUE' line is a catch-all that keeps the original year of birth for those not in these ranges.
    gen = case_when(
      yrbrn %in% 1900:1945 ~ "1",
      yrbrn %in% 1946:1964 ~ "2",
      yrbrn %in% 1965:1979 ~ "3",
      yrbrn %in% 1980:1996 ~ "4",
      TRUE ~ as.character(yrbrn)  
    ),
    # After recoding, the gen variable is converted into a factor with labels for clearer interpretation.
    # Factors are used in R to handle categorical variables.
    gen = factor(gen,
                 levels = c("1", "2", "3", "4"),
                 labels = c("Interwar", "Baby Boomers", "Gen X", "Millennials"))
  )
table(df$gen)

## 
##     Interwar Baby Boomers        Gen X  Millennials 
##         6373        11474         7648         6704

# The dataframe is further updated to recode trust and political interest # note: you could have done it one, integrating above, but I broke it down
df <- df %>%
  mutate(
    # Recoding the 'ppltrst' variable, which seems to measure trust on a scale from 0 to 10.
    # Special codes like 77, 88, 99 are probably used for missing data and are set to NA.
    # Trust levels are categorized as 'Low', 'Mid', and 'High'.
    Capital = case_when(
      ppltrst %in% c(77, 88, 99) ~ NA_character_,
      ppltrst >= 0 & ppltrst <= 3 ~ "Low",
      ppltrst >= 4 & ppltrst <= 6 ~ "Mid",
      ppltrst >= 7 & ppltrst <= 10 ~ "High",
      TRUE ~ as.character(ppltrst)
    ),
    # Recoding 'polintr' variable, which seems to measure political interest.
    # Values of 1 and 2 indicate 'Interested', 3 and 4 'Not Interested'.
    # Special codes like 7, 8, 9 (likely missing data) are set to NA.
    Politically = case_when(
      polintr %in% c(1, 2) ~ "Interested",
      polintr %in% c(3, 4) ~ "Not Interested",
      polintr %in% c(7, 8, 9) ~ NA_character_
    )
  )

df <- df %>%
  mutate(behave = ipbhprp,
         secure = impsafe,
         safety = ipstrgv,
         tradition = imptrad,
         rules = ipfrule) %>%
  mutate(across(c("behave", "secure", "safety", "tradition", "rules"),
                ~ na_if(.x, 7) %>% na_if(8) %>% na_if(9))) %>%
  # Apply the reverse coding
  mutate(across(c("behave", "secure", "safety", "tradition", "rules"), ~ 7 - .x ))

# Now you can calculate 'schwartzauth' after the NA recoding
df$auth <- scales::rescale(df$behave + 
                      df$secure + 
                      df$safety + 
                      df$tradition + 
                      df$rules, to=c(0,100), na.rm=TRUE)


df <- df %>% filter(!is.na(auth))

Let’s add some covariates of interest, which will be our previously recoded lrscale with three categories (left/moderate/right), as well as a cleaned version of ‘how religious’ respondents are (from 0-10). Here, we are testing ideas related to the political right and being more religious as associated to authoritarian attitudes.

df <- df %>%
  mutate(
    polID = case_when(
      lrscale %in% 0:3 ~ "Left",                    
      lrscale %in% 7:10 ~ "Right",                     
      lrscale %in% 4:6 ~ "Moderate",                  
      lrscale %in% c(77, 88, 99) ~ NA_character_      
    ),
   religious = case_when(
      rlgdgr %in% c(77, 88, 99) ~ NA_real_,
      TRUE ~ rlgdgr
    )
  )

Note: In our code above we renamed our variables polID and religious. You can always name variables to whatever you prefer (before the = case_when), notably to more easily track what the variables are and not make typos if you write them out in your models.

Modelling

We will use modelsummary here and specify two models (MLR and MLR with interaction). We will look into the possibility of an interaction between religiousness and ideological self-placement as left, moderate, and right.

First, let’s run our models.

model3 <- lm(auth ~ polID + religious, data = df, weights = weight)
model4 <- lm(auth ~ polID + religious + polID*religious, data = df, weights = weight)

Next, let’s use the modelsummary function to generate our table. Note: remember, as we did in the previous tutorial, the finalized version should have a title and coefficients renamed in terms of how they are displayed. By default you have the variable name + category (when it’s a categorical variable). So, for example, polIDRight as a listed coefficient.

modelsummary(
  list(model3, model4),
  fmt = 1,
  estimate  = c( "{estimate} ({std.error}){stars}",
                "{estimate} ({std.error}){stars}"),
  statistic = NULL)

	(1)	(2)
(Intercept)	55.3 (0.3)***	56.4 (0.3)***
polIDModerate	4.6 (0.3)***	3.4 (0.4)***
polIDRight	7.7 (0.4)***	4.2 (0.7)***
religious	0.9 (0.0)***	0.6 (0.1)***
polIDModerate × religious		0.3 (0.1)***
polIDRight × religious		0.8 (0.1)***
Num.Obs.	23373	23373
R2	0.048	0.050
R2 Adj.	0.048	0.050
AIC	200594.1	200558.6
BIC	200634.4	200615.0
Log.Lik.	−100292.049	−100272.298
RMSE	17.27	17.24

##TASK 1 ANSWER Let’s first interpret the MLR coefficient output before turning to a discussion of the interaction output, which we will also visualize.

polIDModerate (4.6): This coefficient suggests that, comparing individuals with the same religiousness (i.e., what some term “holding constant”), the average outcome for individuals identifying as politically moderate are 4.6 units higher compared to the reference category (in our case, identifying ideologically as on the ‘left’). The “baseline group” refers to the category that is omitted, and is thus interpreted as part of our intercept.
polIDRight (7.7): This coefficient indicates that, comparing individuals with the same religiousness, individuals identifying as politically right are expected to be, on average, 7.7 units higher than the reference category (i.e., identifying ideologically as on the ‘left’) on the authoritarian values scale.
religious (0.9): For the ‘religious’ predictor, a coefficient of 0.9 means that with every one-unit increase in religiousness, there is an associated expected average increase of 0.9 units on the authoritarian values scale, assuming that we are comparing people with the same ideological categorization (i.e., holding ideological self-placement constant).

All three coefficients have ***, indicating a p < 0.001. Meaning: There is less than a 0.1% probability that the observed result is due to chance and we incorrectly reject the null, under frequentist assumptions.

Additional note: When interpreting the intercept (48.7 in the MLR), it represents the expected value of the outcome variable when all the predictor variables are set to their reference levels (so polID as ‘left’, in our case, although you can change that) and, for continuous variables, when they are set to zero (so religiousness as 0, in our case). For categorical variables, the reference level is the one that is left out of the model – i.e., you would not see it displayed in your regression table.

In sum, both models suggest that political identification and religiosity are significant predictors of authoritarian values.

Task 2

Now generate the model4 interaction plot that we did in the tutorial, but again using the German data instead of the French. Interpret.

interaction_plot <- effect("polID*religious", model4, na.rm=TRUE)

plot(interaction_plot,
     main="Interaction effect",
     xlab="Religiousness",
     ylab="Authoritarian attitudes scale")

interaction_plot

## 
##  polID*religious effect
##           religious
## polID             0        2        5        8       10
##   Left     56.40706 57.56775 59.30879 61.04983 62.21053
##   Moderate 59.85063 61.66176 64.37844 67.09513 68.90626
##   Right    60.60237 63.35032 67.47224 71.59416 74.34211

#TASK 2 ANSWER polID = Left: The line for individuals who are left begins at the lowest point on the authoritarian attitudes scale when religiosity is at zero and rises gradually when religiosity increases. This means there is a positive relationship between religiosity and authoritarian attitudes for this group.

polID = Moderate: The moderate line starts higher on the authoritarian attitudes scale than the left when religiosity is at zero. When religiosity increases, there is a positive relationship with authoritarian attitudes increasing.

polID = Right: For people who are politically Right, the line starts significantly higher on the authoritarian attitudes scale even when religiosity is at zero. As religiosity increases, the authoritarian attitudes scale also increases.

Task 3

Use data for the Netherlands and the variable coding for model5 and model6 from the tutorial (i.e., both for the cleaning & recode, as well as the linear model formulas). Do a modelsummary table displaying both model outputs. Interpret the coefficients for the MLR without the interaction (i.e., the first displayed model), and interpret model fit metrics for both models.

netherlands_data <- read_fst("netherlands_data.fst")

df <- netherlands_data

df$weight <- df$dweight * df$pweight
survey_design <- svydesign(ids = ~1, data = df, weights = ~weight)

Multiple linear regression

We will work with our populist attitudes scale based on Norris and Inglehart’s conceptualization and measurement again. So let’s run our code:

Setting up our populist scale

# Setting values greater than 10 to NA
df$trstplt <- ifelse(df$trstplt > 10, NA, df$trstplt)
df$trstprl <- ifelse(df$trstprl > 10, NA, df$trstprl)
df$trstprt <- ifelse(df$trstprt > 10, NA, df$trstprt)

# Creating and rescaling the trust variable
df$trust <- scales::rescale(df$trstplt + df$trstprl + df$trstprt, na.rm = TRUE, to = c(0, 100))

# Here's how you would "flip it" because populist is conceived by N + I as 'anti-trust'
# As Schafer explains there are some issues with that conceptualization, but N + I is also widely applied
df$populist <- scales::rescale(df$trust, na.rm = TRUE, to=c(100,0))

Now, let’s suppose we read literature about the importance of social capital, political interest, and generational trends for understanding populism.

Let’s recode the variables and see if that is supported.

df <- df %>%
  mutate(
    cohort = ifelse(yrbrn < 1930 | yrbrn > 2000, NA, yrbrn),
    # Recoding generational cohorts based on the year of birth (yrbrn).
    # The year of birth is categorized into different generational cohorts.
    # Interwar (1900-1945), Baby Boomers (1946-1964), Gen X (1965-1979), Millennials (1980-1996).
    # The 'TRUE' line is a catch-all that keeps the original year of birth for those not in these ranges.
    gen = case_when(
      yrbrn %in% 1900:1945 ~ "1",
      yrbrn %in% 1946:1964 ~ "2",
      yrbrn %in% 1965:1979 ~ "3",
      yrbrn %in% 1980:1996 ~ "4",
      TRUE ~ as.character(yrbrn)  
    ),
    # After recoding, the gen variable is converted into a factor with labels for clearer interpretation.
    # Factors are used in R to handle categorical variables.
    gen = factor(gen,
                 levels = c("1", "2", "3", "4"),
                 labels = c("Interwar", "Baby Boomers", "Gen X", "Millennials"))
  )
table(df$gen)

## 
##     Interwar Baby Boomers        Gen X  Millennials 
##         3967         6359         4684         2803

# The dataframe is further updated to recode trust and political interest # note: you could have done it one, integrating above, but I broke it down
df <- df %>%
  mutate(
    # Recoding the 'ppltrst' variable, which seems to measure trust on a scale from 0 to 10.
    # Special codes like 77, 88, 99 are probably used for missing data and are set to NA.
    # Trust levels are categorized as 'Low', 'Mid', and 'High'.
    Capital = case_when(
      ppltrst %in% c(77, 88, 99) ~ NA_character_,
      ppltrst >= 0 & ppltrst <= 3 ~ "Low",
      ppltrst >= 4 & ppltrst <= 6 ~ "Mid",
      ppltrst >= 7 & ppltrst <= 10 ~ "High",
      TRUE ~ as.character(ppltrst)
    ),
    # Recoding 'polintr' variable, which seems to measure political interest.
    # Values of 1 and 2 indicate 'Interested', 3 and 4 'Not Interested'.
    # Special codes like 7, 8, 9 (likely missing data) are set to NA.
    Politically = case_when(
      polintr %in% c(1, 2) ~ "Interested",
      polintr %in% c(3, 4) ~ "Not Interested",
      polintr %in% c(7, 8, 9) ~ NA_character_
    )
  )

df <- df %>%
  mutate(behave = ipbhprp,
         secure = impsafe,
         safety = ipstrgv,
         tradition = imptrad,
         rules = ipfrule) %>%
  mutate(across(c("behave", "secure", "safety", "tradition", "rules"),
                ~ na_if(.x, 7) %>% na_if(8) %>% na_if(9))) %>%
  # Apply the reverse coding
  mutate(across(c("behave", "secure", "safety", "tradition", "rules"), ~ 7 - .x ))

# Now you can calculate 'schwartzauth' after the NA recoding
df$auth <- scales::rescale(df$behave + 
                      df$secure + 
                      df$safety + 
                      df$tradition + 
                      df$rules, to=c(0,100), na.rm=TRUE)


df <- df %>% filter(!is.na(auth))

df <- df %>%
  mutate(
    polID = case_when(
      lrscale %in% 0:3 ~ "Left",                    
      lrscale %in% 7:10 ~ "Right",                     
      lrscale %in% 4:6 ~ "Moderate",                  
      lrscale %in% c(77, 88, 99) ~ NA_character_      
    ),
   religious = case_when(
      rlgdgr %in% c(77, 88, 99) ~ NA_real_,
      TRUE ~ rlgdgr
    )
  )

df <- df %>%
  mutate(religion = case_when(
    rlgblg == 2 ~ "No",
    rlgblg == 1 ~ "Yes",
    rlgblg %in% c(7, 8, 9) ~ NA_character_,
    TRUE ~ as.character(rlgblg)
  ))

# check
table(df$religion)

## 
##    No   Yes 
## 10913  6750

df <- df %>%
  mutate(ID = case_when(
    lrscale >= 0 & lrscale <= 4 ~ "Left",
    lrscale >= 6 & lrscale <= 10 ~ "Right",
    lrscale > 10 ~ NA_character_,  # Set values above 10 as NA
    TRUE ~ NA_character_  # Ensure value 5 and any other unexpected values are set as NA
  ))
table(df$ID)

## 
##  Left Right 
##  5449  7010

model5 <- lm(auth ~ religion + ID + gen, data = df, weights = weight)
model6 <- lm(auth ~ religion + ID + gen + religion*gen, data = df, weights = weight)

modelsummary(
  list(model5, model6),
  fmt = 1,
  estimate  = c( "{estimate} ({std.error}){stars}",
                "{estimate} ({std.error}){stars}"),
  statistic = NULL,
  coef_omit = "Intercept")

	(1)	(2)
religionYes	7.2 (0.3)***	5.7 (0.7)***
IDRight	4.2 (0.3)***	4.3 (0.3)***
genBaby Boomers	−5.2 (0.4)***	−5.9 (0.6)***
genGen X	−7.7 (0.4)***	−8.8 (0.6)***
genMillennials	−8.4 (0.5)***	−9.7 (0.6)***
religionYes × genBaby Boomers		1.1 (0.8)
religionYes × genGen X		2.3 (0.9)**
religionYes × genMillennials		2.9 (1.0)**
Num.Obs.	12116	12116
R2	0.124	0.125
R2 Adj.	0.124	0.125
AIC	101219.3	101213.5
BIC	101271.2	101287.5
Log.Lik.	−50602.672	−50596.757
RMSE	15.27	15.26

##TASK 3 ANSWER - religonYes (7.2): People who are religious score on average 7.2 points higher on the dependent variable than those who are not.

IDRight (4.2): People who are politicaly right, scored 4.2 points higher on the dependent variable than those who do not identify as politically right.
genBaby Boomers (-5.2)*: Baby Boomers score on average 5.2 points lower on the dependent variable than the reference generational cohort.
genGen X (-7.7)*: Generation X individuals score 7.7 points lower on the dependent variable than the reference generational cohort.
genMillennials (-8.4)*: Millennials score 8.4 points lower on the dependent variable than the reference generational cohort.

All coefficients have ***, indicating a p < 0.001. Meaning: There is less than a 0.1% probability that the observed result is due to chance and we incorrectly reject the null, under frequentist assumptions.

Task 4

Produce the model7 interaction plot from the tutorial, but again using the Netherlands data. Interpret.

model7 <- lm(auth ~ + cohort + polID + cohort*polID, data = df, weights = weight)
interact_plot(model7, pred = cohort, modx = polID, jnplot = TRUE)

#TASK 4 ANSWER

Left (solid blue line): For individuals identifying as Left, there appears to be a very slight, almost flat, downward trend in authoritarian attitudes over the generations. It suggests that the younger generations identifying as Left have a slightly lower auth score compared to older generations.

Moderate (dashed orange line): Those who identify as Moderate show a clearer downward trend. As the cohorts get younger, the auth score decreases more noticeably than the Left.

Right (dotted green line): The Right political identification group shows the steepest downward trend. This suggests that younger generations who identify as Right have significantly lower authoritarian attitudes than older generations.

Task 5

Produce the model8 interaction plot from the tutorial, but again using the Netherlands data. Interpret.

model8 <- lm(auth ~ religious + ID + religious*ID, data = df, weights = weight)
interact_plot(model8, pred = religious, modx = ID, jnplot = TRUE)

#TASK 5 ANSWER

People who identify as politically Left: There is a positive relationship between religiosity and authoritarian attitudes. As religiosity increases, so does the authoritarian score.

People who identify as politicaly Right: The relationship is also positive, and the slope of the dashed orange line is steeper than that of the Left, suggesting a stronger association between religiosity and authoritarian attitudes for those on the Right.