September 13, 2011
Lecture # 3 (Chap 1 & 2 continued…)
• To use at home, log in through lib access at McMaster library website and
than try and use it.
• Press tools and press choose working directory. Than look for the assignment.
Then cut and paste document name “slid….” Into R studio.
• Ie of command: mean(wgsal42)
Cross Tabulations (Sep 13)
• Cross Tabulations: They are tabular summaries for 2 variables.
• One variable represented by row heads
• The other variable represented by column heads
• Information for both variables entered in table cells
• In R we use the xtabs ( ) function.
Example (Cross Tabulations)
• Adapted from Pedhauzur (1997). Suppose that 7 out of 10 males are
admitted to an engineering school while 4 out of 10 females are admitted
Sex + (Male)
• Core Graphs
Ex: histograms, scatter diagrams, etc…
• Speciality graphs
-Combine elements from core graphs to display data in unique ways
Ex: bar graphs, pie charts, etc…
• 3D graphs
-Displays data in 3d information
Frequency Histograms September 13, 2011
• Horizontal axis
-Identifies upper and lower class limits of data classes
• Vertical axis
-Shows number of observations in each class (absolute frequencies)
-Shows ratio of class frequency to class width (relative frequencies)
-Represent corresponding class frequencies by area or by height (if all