R notes for Activity 27-6: Exam Score Improvements
Okay, more data. Let's load it in.
ExamScores = read.csv("/home/rebelsky/Stats115/Data/ExamScores.csv")
They wouldn't give us more NA values, would they?
> summary(ExamScores)
Student Exam1 Exam2
S01 : 1 Min. :72.00 Min. :50.00
S02 : 1 1st Qu.:82.25 1st Qu.:68.50
S03 : 1 Median :88.50 Median :80.00
S04 : 1 Mean :87.38 Mean :78.65
S05 : 1 3rd Qu.:95.00 3rd Qu.:91.00
S06 : 1 Max. :98.00 Max. :97.00
(Other):18 NA's : 1.00
Yes, I guess they would. Let's get rid of it.
ExamScores = na.omit(ExamScores)
plot(ExamScores$Exam1, ExamScores$Exam2)
27-6 b. Yet another correlation cofficient
You should be able to compute this one on your own.
27-6 d. Changing exam 1 grades.
You can change the exam 1 grades en masse
with
ExamScores$Exam1 = ExamScores$Exam1 - 10
27-6 f. Changing exam 2 grades
If you look at 27-6 d., you should be able to figure out how to double
the grades on exam 2.
exam1 = c(...)
exam2 = exam1 + 10
plot(exam1, exam2)
cor(exam1,exam2)
We can continue to use the exam 1 grades from part h. We just need
to change the way we compute the exam 2 grade.
exam2 = exam1 * 2
plot(exam1, exam2)
cor(exam1,exam2)
