By the end of this lesson you will be able to
explain/calculate the following:
1. Types of Data
2. Graphical Representation of Data
Types of Data
All data can be divided into two major groups:
categorical (or qualitative) and numerical (or quantitative).
Placed in categories.
• nominal — the information is divided
into subgroups;
for example, eye colour (hazel, blue,
green).
• ordinal — the categories are in some
type of ranked order;
for example, pizza sizes (family, large,
medium, small).
Types of Data
All data can be divided into two major groups:
categorical (or qualitative) and numerical (or quantitative).
Data are in numerical form.
• discrete — the data can take only
certain exact values, usually whole
numbers, and are associated with
counting; for example, the number
of SMS calls sent.
• continuous — the data can take
any value within a certain range,
and are associated with measuring;
for example, the time taken to read
Harry Potter and the Chamber of
Secrets.
Graphs - Key Features
 Key features of graphs include:
1.
2.
3.
4.
5.
a bold and appropriate title
clearly-labelled and evenly scaled axes
an attractive use of line, shading and colour
a key or legend for any symbols used, with roundings noted
a source of data which clearly identifies the origin of the
information.
Bar and Column Graphs
 Bar and column graphs are often used to represent




categorical data
Each bar (or column) represents a single category
or an observation
Its length (or height) shows the frequency of each
category
The bar graph has frequencies on the horizontal
axis
The column graph has frequencies on the
vertical axis
Worked Example
Compound and Multiple Graphs
 When comparing two or more sets of data relating
to the same topic at the same time, the following
are used:
i.
ii.
compound column graphs and bar graphs
multiple column graphs and bar graphs.
Pie Graphs
 Pie graphs (or sector graphs or pie charts or
circular graphs) are mostly used to represent
categorical data.
 The size of the sector is proportional to the size
of that category, as compared to the total.
Worked Example
Pictographs
 Pictographs (or picture graphs or pictograms) allow
data to be displayed in a novel way using
illustrations or symbols
 A key or legend is always used to show the
number of items each symbol represents.
 Half pictures can be used to represent half of the
data.
 However, smaller fractions such as one-third or one-
quarter may be quite difficult to illustrate using
pictographs
Worked Example
Dot Plots
 Dot-plots are similar to pictographs.
 Each observation is represented by a single dot.
 A good feature of the dot-plot is that it can be
constructed while in the process of collecting the data.
 A horizontal axis is prepared by writing in possible
values of observations or categories, and then the
collection of data begins.
 Each time a certain value is observed, a dot is placed
in the corresponding column.
 Provided that the dots are placed neatly in columns
and are evenly spaced, by the end of the experiment
the data collected are also represented graphically
Worked Example