Multilevel Analysis (9/17) Exercise 1

Exercise 1: Draw a scatter plot of the variables written and course scores from the data set Gcsemv{mlmRev} and superimpose another scatter plot on it using mean written and mean course scores by school.

1 compute averages by school

library(mlmRev)
dta_a <- Gcsemv %>% 
         group_by(school) %>% 
         summarize(ave_written = mean(written, na.rm=TRUE),
                   ave_course = mean(course, na.rm=TRUE))

2 superimpose two plots

ggplot(data=Gcsemv, aes(x=written, y=course)) +
 geom_point(color="skyblue") +
 stat_smooth(method="lm", formula=y ~ x, se=F, col="skyblue") +
 geom_point(data=dta_a, aes(ave_written, ave_course), color="steelblue") +
 stat_smooth(data=dta_a, aes(ave_written, ave_course),
             method="lm", formula= y ~ x, se=F, color="steelblue") +
 labs(x="Total score on written paper", 
      y="Total score on coursework paper") +
 theme_bw()