Bar Charts, Histograms
and Pie Charts
Slideshow 52, Mathematics
Mr Richard Sasaki
Room 307
Objectives
•
Understand the differences between bar
charts and histograms and types of data
•
Be able to read tables and create histograms
and bar charts
Note: For the next few lessons, you will need a
protractor and calculator.
Bar Charts and Data Types
Bar charts and simple histograms hold valid data
values vs their frequency (the amount of times
they were chosen).
Bar charts hold categorical and quantitative discrete
data. There are gaps between bars.
Bar charts have titles, and
both axes should have labels.
Which colour was the
Pink
most popular?
How many people
56
were surveyed?
Type of Animal
100
The cat
An “Other” section exists.
Histograms
Histograms hold quantitative continuous data. For
this reason, there are no gaps between bars.
Histograms also have titles
and their axes are labelled.
Notice, values of heights
are on the edges of bars,
not in the centre.
As the data is shown as ranges, it is impossible to
recover exact heights of people. Another way of
showing data from a histogram is a frequency polygon.
It connects where the centres of the bars are.
Answers
No.
40 + 35 = 75
71 ~79 accepted
The number of people in each
Pie Charts
Pie charts are hard to work with as a protractor is
necessary and we need to divide data into
amounts of degrees. Calculators and computers
make nasty calculations easier.
The circle has 360 degrees…
So if we had 360 pieces of data,
𝑜
each piece would represent 1 .
180 pieces of data means each
𝑜
360𝑜
piece is 2 .
For 𝑥 pieces of data, each 360
piece is… 𝑥
𝑜
Pie Charts
Example
A random sample of students from GKA are asked
how they arrive at school.
Method Frequency
There were 100 students
Bicycle 58 208.8o
surveyed. This means on the pie On Foot 18 64.8o
chart, 1 student represents 3.6o. By car 7 25.2o
By bus 15 54o
Other 2
Other 2 7.2o
Bicycle We should measure to the
nearest degree. Let’s check it
On Foot
58
𝑜
adds
up
to
360
.
18
209 + 65 + 25 + 54 + 7 = 360
Skills Acquired
We now know…
How to calculate the mean, median, mode and
range for discrete data
How to construct bar charts for categorical and
quantitative discrete data
How to construct histograms with quantitative
continuous data
How to construct pie charts for all data types
We can now use these concepts for our projects.
Survey
You now need to construct a survey to ask to
students in your class, along with other students in
the school.
I recommend that you work as a pair. The minimum
amount of work will be adjusted depending on how
many of you are working together.
Min # of People to survey for each question
# of Questions: 1
2
3
4
5
1 person 80
15
10
35
20
2 people 160 70
30
20
40
3 people 240
105
60
45
30
Survey
It is your choice what question you ask, how many
results it has, what type of data the results are. You
may choose to get your results from this class,
randomly from this grade, from junior high school
or from the high school. You may wish to compare
results depending on the grade.
Each question you ask must have data collected
placed into an appropriate frequency table and
results are to be shown in either a stem and leaf
diagram, a bar chart, a histogram or a pie chart.
If the data is quantitative discrete, you may wish to
find the mean, median, mode and range.
Survey
If you wish to compare results for grades (for
example, you want to ask the same question to
Grade 7 to Grade 11, you should consider this to be
two questions and results should be recorded in the
same way so you can compare.
Have a think about which questions you would like
to ask!
This will be due on Wednesday, 9th March. Good
luck!