Histograms

1
Histograms
Objectives
A Grade Interpret a histogram
with unequal class intervals
Prior knowledge
Draw a Histogram diagram
2
Histograms
Finding Frequencies
10 x 1.5 15
20 x 1 20
20 20 20 15 75
2
1
10
20
How many lengths are in the class interval 40cm
to 60cm?
20 x 1 20
How many lengths are in the class interval 30cm
to 40cm?
10 x 2 20
75
What is the total frequency?
Repeat for the other bars.
3
Histograms
From this histogram you could be asked further
questions
Estimate how many people between the ages of 35
and 55 surf.
Identify the area of the bars to which this
applies.
Remember frequency is the area
1.2
1 3
35
55
5
Find the area separately of each bar
15
5 1.2 6
Estimate of the frequency 6 5 11
15 1 5 3
4
Histograms
Frequency 1518172025205 120
Estimate the median from this histogram
median position 60
5 4 20
5 3.6 18
Where is this?
5 3.4 17
10 2.5 25
10 2 20
The median is approximately 137.5 cm
10 0.5 5
15 1 15
60
15
33
50
Find the total frequency, then find which class
interval it is in, draw a line in the bar where
the median is represented to find where it is
on the x axis