Instructions: Copy the entire R work into the "R document editor" save it and email it with any graphical output. Also make a print out of your work and turn it in with the final exam.
(a) Start up R.
(b) Type "> getwd()" without the ">" symbol.
(c) Type "Sys.time()"
(d) Type "Sys.info()"
(e) Type in any free responses as comments using #.
1. The following data represent the number of days of absences and the final average grade in a particular class at a certain university.
| Number of Absences Xi |
Average Grade Yi |
| 0 |
89.2 |
| 0 |
94 |
| 1 |
91.3 |
| 2 |
83.5 |
| 3 |
81.1 |
| 4 |
73.9 |
| 4 |
78.2 |
| 5 |
68.3 |
| 5 |
65 |
| 6 |
64.3 |
| 7 |
71.8 |
| 8 |
58.5 |
| 9 |
45.5 |
a) Using "R", draw a boxplot of the average grades
b) Using "R", draw a scatter plot with appropriate x and y labels
c) Does the scatter plot suggest that the least-square line is a good predictor?
d) Using "R", compute the least-square line for predicting the average grade.
e) What is the predicted average grade when the number of absences is 6?
2. Consider the data set "gala" from the following source:
> install.packages("faraway")
>library(faraway)
> data(gala)
a) Describe the nature of the data set and the variable names with appropriate units. You may use the commands "head()" and/or "??".
b) Perform numerical summary analyses - means, standard deviations, five-number summaries, etc. for the variables "Species" and "Elevation". (You can extract these variables by the commands x<-gala$Species and y<-gala$Elevation)
c) Perform graphical summary analyses on x and y
- one variable boxplots, histograms, etc.
- two variable scatterplots.