Histograms and Ogives — Part 2: Cumulative frequency, ogive, median and quartiles: visual lesson, ICSE Class 10 Mathematics

Lesson

Histograms and Ogives, Part 2

The ogive turns a running total into a graph that answers questions about the middle of the data.

In this lesson you will

Make a less-than cumulative frequency table
Draw the less-than ogive
Read the median, quartiles and inter-quartile range
Read the number of observations above, below or between marks

less-than ogive

The ogive passes through $(0, 0)$, $(10, 6)$, $(20, 16)$, $(30, 24)$, $(40, 32)$, $(50, 36)$ and $(60, 40)$.

Concept

What you will be able to do

Make a cumulative frequency table
Draw the less-than ogive
Read the median, quartiles and inter-quartile range
Read counts above, below and between marks

The plan for part 2.

Concept

Cumulative frequency

The less-than cumulative frequency of a class is the number of observations below its upper boundary: add the frequencies from the first class up to that class.

The words used on the ogive.
Word	Meaning
Frequency	observations in one class
Cumulative frequency	running total: observations in this class and all classes before it
Less-than cumulative frequency	observations below the upper boundary of the class
Ogive	the line graph of upper boundaries against cumulative frequencies

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