Histograms
The following table shows the ages of 25 children on a school bus:
Age Frequency
5-10 6
11-15 15
16-17 4
> 17 0
If we are going to draw a histogram to represent the data, we first need to find the class boundaries. In this case they are 5, 11, 16 and 18. The class widths are therefore 6, 5 and 2.
The area of a histogram represents the frequency.
The areas of our bars should therefore be 6, 15 and 4.
Remember that in a bar chart the height of the bar represents the frequency. It is therefore correct to label the vertical axis 'frequency'.
However, as in a histogram, it is the area which represents the frequency.
It would therefore be incorrect to label the vertical axis 'frequency' and the label should be 'frequency density'.
To draw a histogram you will need to work out the frequency density. The frequency density can be calculated by using the following formula:
Frequency density = frequency ÷ class width
The class width is basically the width of the group.
The frequency density goes up the y-axis, and the area of each bar will represent the frequency.
The following table shows the ages of 25 children on a school bus:
Age Frequency
5-10 6
11-15 15
16-17 4
> 17 0
If we are going to draw a histogram to represent the data, we first need to find the class boundaries. In this case they are 5, 11, 16 and 18. The class widths are therefore 6, 5 and 2.
The area of a histogram represents the frequency.
The areas of our bars should therefore be 6, 15 and 4.
Remember that in a bar chart the height of the bar represents the frequency. It is therefore correct to label the vertical axis 'frequency'.
However, as in a histogram, it is the area which represents the frequency.
It would therefore be incorrect to label the vertical axis 'frequency' and the label should be 'frequency density'.
Frequency density = frequency ÷ class width
A histogram is usually drawn when you have continuous data and the groups in the frequency table are of unequal size
To draw a histogram you will need to work out the frequency density. The frequency density can be calculated by using the following formula:
Frequency density = frequency ÷ class width
The class width is basically the width of the group.
The frequency density goes up the y-axis, and the area of each bar will represent the frequency.
Thanks. Very helpful
ReplyDeleteWelcome! By the way, where are u from? and what u do?
Deletehow do i calculate frequency density from my frequency table
ReplyDeletehow do i calculate frequency density from my frequency table
ReplyDeleteFrequency density is given by
DeleteFrequency density= frequency ÷ class width
What is frequency Density?
ReplyDeleteGive the relation between raw and central moments
ReplyDeletehow do i figure out frequency from the frequency dencity? how do i make the formula have frequency as the subject?
ReplyDeleteit's going to be frequency=classwidth*frequency density.
Delete