analysis and presentation of data_graphical representation
TRANSCRIPT
Analysis and Presentation of Data
Graphical Representation
Dr. Prabath KarunanayakeMBBS, MBA in HRM, PGDipPsych, PGDipOHSFormer Head of HR, Access Engineering PLC
15th December 2013
A graph is a visual representation of a relationship between two or more variables
A graph generally takes the form of a two-dimensional figure◦ Although there are three-dimensional
graphs available, they are usually too complex to understand easily
A graph is not always the most appropriate tool to present information◦ Sometimes text or a data table can
provide a better explanation to the readers
What is a graph?
Knowing what type of graph to use with what type of information is crucial◦ Depending on the nature of the data
some graphs are more appropriate than others
Graphs are used because they◦ are quick and direct◦ highlight the most important facts◦ facilitate understanding of the data◦ can convince readers◦ can be easily remembered
accurately shows the factsgrabs the reader's attentioncomplements or demonstrates
arguments presented in the texthas a title and labelsis simple and unclutteredshows data without altering the
message of the dataclearly shows any trends or
differences in the datais visually accurate (i.e., if one chart
value is 15 and another 30, then 30 should appear to be twice the size of 15)
Qualities of a good graph
When not to use graphs
When the data are very dispersed
When there are too few data (only one, two or three data points)
When the data are very numerous
When the data show little or no variations
Define your target audience: Ask yourself the following questions to help you understand more about your audience and what their needs are: ◦ Who is your target audience?◦ What do they know about the issue?◦ What do they expect to see?◦ What do they want to know?◦ What will they do with the information?
Guidelines to create a better graph
Determine the message(s) to be transmitted: Ask yourself the following questions to figure out what your message is and why it is important:◦ What do the data show?◦ Is there more than one main message?◦ What aspect of the message(s) should be
highlighted?◦ Can all the messages be displayed in the
same graphic?
Use appropriate terms to describe your graph: Consider the following appropriate terms when labelling the graph or describing features of it in the text:If your graph... Use the following terms...
describes components
share of, percentage of the, smallest, the majority of
compares itemsranking, larger/smaller than, equal to
establishes a time series
change, fluctuation, rise, growth/decline, increase/decrease
determines a frequency
range of, concentration of, most of, distribution of x and y by age
analyses relationships
Increase/decrease of x with y, vary with, despite, correspond to, relate to
Select the most appropriate type: Experiment with different types of graphs and select the most appropriate, based on the target audience and message to be conveyed:◦ circle graph/pie chart (description of
components)◦ horizontal bar graph (comparison of items
and relationships, time series)◦ vertical bar graph (comparison of items
and relationships, time series, frequency distribution)
◦ line graph (time series and frequency distribution)
◦ scatterplot (analysis of relationships)
Bar graphs usually present categorical and numeric variables grouped in class intervals
They consist of an axis and a series or labeled horizontal or vertical bars.
The bars depict frequencies of different values of a variable or simply the different values themselves.
The numbers on the x-axis of a bar graph or the y-axis of a column graph are called the scale
Bar Graphs
A line graph is a visual comparison of how two variables—shown on the x- and y-axes—are related or vary with each other.
It shows related information by drawing a continuous line between all the points on a grid.
The y-axis in a line graph usually indicates quantity (e.g., dollars, litres) or percentage, while the horizontal x-axis often measures units of time
As a result, the line graph is often viewed as a time series graph
Line Graphs
When drawing a line, it is important that you use the correct scale. Otherwise, the line's shape can give readers the wrong impression about the data.
A pie chart is a way of summarizing a set of categorical data or displaying the different values of a given variable (e.g., percentage distribution)
This type of chart is a circle divided into a series of segments and each segment represents a particular category
The area of each segment is the same proportion of a circle as the category is of the total data set.
Circle graphs/pie charts usually show the component parts of a whole
Circle Graphs (Pie Charts)
The scatter plot is widely used to present measurements of two or more related variables.
It is particularly useful when the variables of the y-axis are thought to be dependent upon the values of the variable of the x-axis (usually an independent variable).
In a scatter plot, the data points are plotted but not joined and the resulting pattern indicates the type and strength of the relationship between two or more variables
Scatter plot
