2. Displaying Univariate Data
Frequency Table: Used to organise data so that it
is more manageable.
Frequency can either be counted or taken as a
percentage
A frequency table displays the data in a compact
form and also tells us something about how the
values are distributed
K McMullen 2012
3. Displaying Univariate Data
Bar charts: used to display categorical data or
discrete numerical data
The variable is usually plotted on the horizontal
axis
The frequency (or percentage frequency) is
usually displayed on the vertical axis
The bars of equal width and have equal spaces
between them
There is one bar for each category
The height of the bar gives the frequency (or
percentage frequency)
K McMullen 2012
4. Displaying Univariate Data
Segmented bar charts: a variation of the bar
chart where the bars are stacked on top of one
another to give a single bar with several
components.
The lengths of the segments is determined by the
frequencies
The height of the bar gives the total frequency (
total in data set or 100% for percentage
segmented bar charts)
Should only be used for a relatively small number
of components (5 maximum)
Percentage segmented bar charts are more
useful when comparing bivariate data (two
variables) K McMullen 2012
5. Displaying Univariate Data
Dot Plots: Used to display categorical data or
discrete numerical data with the variable along
the horizontal axis and each dot above it
representing one piece of data
Best used for small sets of data and when the
data values are relatively close together (small
range)
K McMullen 2012
6. Displaying Univariate Data
Stem plots: each value of the data set it split into
two parts:
Stem: derived from the first digit(s)
Leaf: the last digit
The data is displayed in order
Always use a key indicating how to interpret the
plot
K McMullen 2012
7. Displaying Univariate Data
Histograms: Used to display discrete and
continuous numerical data and is better used for
large data sets as data can be placed into
intervals.
The variable is usually plotted on the horizontal
axis
The frequency (or percentage frequency) is
usually displayed on the vertical axis
The height of the bar gives the frequency
The bars have no spaces between them
There is one bar for each class interval
K McMullen 2012
8. Displaying Univariate Data
Box plots: Used to display numerical data and is
a graphical representation of the 5 number
summary
Displays the location, spread and general shape
of a distribution
Can be drawn either vertically or horizontally
Must always include a scale and the components
of the 5 number summary must be clearly labelled
Parallel box plots are used when you are
comparing different groups (eg. Study scores of
males compared to females)
K McMullen 2012
