LECTURE 2
Descriptive Statistics: Tabular and Graphical Methods
This lecture covers material on frequency and relative frequency distributions, bar
graphs, dot plots, histograms and cumulative distributions.
Microsoft Excel is used
for some applications.
Read:
Chapter 2, Sections 2.1, 2.2.
Frequency Distributions:
A frequency distribution is a tabular summary of data showing the frequency of items
in each of several nonoverlapping classes.
For qualitative data, as shown in Tables 2.1 and 2.2, each class is defined by the
name or label (in this case names of soft drinks).
For quantitative data, defining nonoverlapping classes requires three steps (as shown
in pp. 34 35):
1. Select the number of classes.
Note:
A rule of thumb in determining the number of classes is to take the square root
of the sample size (i.e., number of observations in the sample or
n
), and round
it upwards to the nearest integer.
Example: If the number of observations or
n
= 20, then square root of 20 =
4.47.
Rounding upwards to the next integer, number of classes = 5.
2. Determine width of each class.
3. Determine the class limits.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Summer '08
 SINGER
 Frequency, Frequency distribution, Bar chart, Histogram, relative frequency

Click to edit the document details