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.