This video is part 1 in a series of videos
on graphing in excel 2010.
This part is on introduction to pie charts
and bar graphs.
For this part I will be introducing pie charts
and bar graphs by using the data on tuition
and fees of the CU engineering freshmen in
the school year 2011 to 2012.
That data I have listed in a spreadsheet.
As you can see I have two sets of data.
One for the in state students and another
for the out of state students.
The only different between these to data sets
is the actual tuition values.
As you can see the tuition values are the
only numerical difference.
All of the fees are exactly the same.
The reason I am pointing this out to you will
be made apparent as soon as we compare the
pie charts for the in state and out of state
students.
The pie chart for the in state students is
here.
As you can see a pie chart is separated into
different slices and each slice represents
a specific comparison value.
For example the large blue slice here represents
the tuition which is listed in the legion.
The tuition as you can see in the chart is
$12,650.
If I hover my mouse over the slice it will
give information about that particular slice.
For example it says that the series is in
state students, the point or comparison value
is tuition and the value of this is $12,650.
It also says that this makes up 45% of the
total payment made for in state students.
This goes on for the rest of the slices.
The dorm when assuming a double dorm room
with the 19 meal plan is $11,278 which is
40% of what the in state student will pay.
If I move on to the non resident students
you can see that the pie chart looks much
different.
In this case the tuition which is $31,300
is 67% of what the out of state student will
pay.
Because of this larger chunk it makes it seem
like the out of state student pay less for
the rest of the fees even though those values
are exactly the same.
The same value which is $11,278, the fee payment
for the dorm, only takes up 24% of what the
out of state student will pay rather than
the 40% that the in state student will pay.
If you want to compare specific values rather
than just percentages of the value then you
want to use a bar graph.
This bar graph which has a normal scaling
of the values on the y-axis compares the specific
tuition and fees of both the in state which
is blue and the out of state which is red.
As you can see the form with the meals, the
student gold insurance, and everything else
are exactly the same.
The biggest difference comes with the tuition
payments where the out of state student pays
more than double what the in state student
pays.
Because the values are so small for the rest
of these fees it is nearly impossible to see
what they are on this chart.
If you change the scaling on the y-axis however
you can get a better look at the rest of those
fees.
The scaling on this axis is now a log based
two scale which means that each jump on the
axis goes up double of the previous one.
On here it looks like the difference between
the tuition of the in state and out of state
students is not very big even though we know
that the out of state student pays more than
double what the in state student pays.
This does make it easier to see these lower
values where you can continue to see that
they are exact same value for the in state
and out of state students.
Although both of these charts have the ability
to represent the same data there are obvious
differences between them.
For example the bar graph represents the data
in a series of columns while the pie chart
shows it in slices.
Aside from this obvious difference there are
still some more subtle ones.
For example for the pie chart you can only
see one set of information at a time.
Either the in state students or the out of
state students.
For the bar graphs you have the ability to
compare them side by side on the same chart.
Another con of using both the pie chart and
the bar graph is that you can only use it
with individual comparison points.
Tuition, dorm, insurance, fees, etc.
Neither of these work when you are working
with a continuous data set.
To recap on the pros and cons of each.
For pie charts the pros are that it shows
relationship between related data.
For example it shows the relationships between
the tuition and the fees of the in state and
out of state student.
It also creates a visual representation for
percentages as a whole.
For example the whole amount that an in state
student pays only 40% of that is their dorm
payment while for the out of state student
67% of what they pay is just for tuition.
Another pro is that it can be formatted to
display values or even percentages.
In my case I chose to use values because that
was more useful to my example but if you are
going to be displaying voting trends it may
be more useful to show percentages to say
that 50% of the voters chose one options over
another.
Cons of using a pie chart is that it doesn't
display the total value that the percentages
represent.
In our case the total value that the in state
student paid was about $28,000 while the total
value the out of state students paid was $46,000.
It can also be misleading on values when comparing
between two charts in the case of the in state
and out of state students it made it seem
like the out of state students paid less on
the fees than the in state students.
Pie charts cannot also compare separate sets
of information using the same comparison values
on a single chart which is why I needed to
have a separate chart for the in state students
and the out of state students.
Pie charts are only effective with individual
comparison values rather than a continuous
data set.
The pros of a bar graph is that it displays
differences between the comparison points
similar to a pie chart.
It also allows for a comparison between related
sets of information using the same comparison
points like how we were able to graph the
in state and out of state student tuition
information on the same chart.
It can be formatted to display actual values
though in my case I did not do that since
there was a large amount of data and having
the numbers attached would have made it more
confusing to look at.
Bar graphs you can also change the scaling
of the axis to better view the data.
Cons of bar graphs is that if there was large
size difference between values in comparison
points it may be difficult to see the smaller
values which is why I had a separate chart
with a different scaling on the axis to better
see the smaller values.
Bar graphs are also not as visually pleasing
as a pie chart.
This may not seem as important to you now
but if you are making a formal presentation
you want to have a visually pleasing presentation
to keep the viewer interested in what you
are presenting.
Bar graphs are also only effective with individual
x-values rather than a continuous data set.
