Grading the professor
download.file("http://www.openintro.org/stat/data/evals.RData", destfile = "evals.RData")
load("evals.RData")
Exploring the data
Exercise 1
Is this an observational study or an experiment? The original research question posed in the paper is whether beauty leads directly to the differences in course evaluations. Given the study design, is it possible to answer this question as it is phrased? If not, rephrase the question.
This is an observational study. Since this is an observational study, the variables can not be controlled and therefore it would be rather difficult to answer the current question. A better question might be: “Does beauty have an affect on course evalution scores?”
Exercise 2
Describe the distribution of score. Is the distribution skewed? What does that tell you about how students rate courses? Is this what you expected to see? Why, or why not?
hist(evals$score)
The distribution of score is definitely skewed left. I am assuming the scoring is from 1 to 5. I would assume that most evalutions would be closer to 5 because professors that typically rate low might be let go for reasons that led to such a low score. It wouldn’t be a good school to attend if half the professors rated low.
summary(evals$score)
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## 2.300 3.800 4.300 4.175 4.600 5.000
The median sits at 4.3 and the mean is shifted left at 4.175.
Exercise 3
Excluding score, select two other variables and describe their relationship using an appropriate visualization (scatterplot, side-by-side boxplots, or mosaic plot).
plot(evals$age ~ evals$cls_perc_eval)