Absolute frequency

Your observation

You have made an observation of 10 students in your class.

In the table below, you can see how tall they are.

 

Name	Height
James	176 cm
Oliver	172 cm
Emma	160 cm
Sophia	161 cm
William	170 cm
Ava	167 cm
Benjamin	156 cm
Mia	160 cm
Lucas	168 cm
Charlotte	158 cm

 

 

Absolute frequency and intervals

Absolute frequency means how many times an observation appears in a data set.

In our case, most observations occur only once, so we can divide them into intervals.

We divide them into three intervals with 10 cm each.

Now we can see how often different heights appear.

 

Height cm	150-159	160-169	170-179
Absolute frequency h(x)	2	5	3

 

As you can see, most students are between 160–169 cm tall.

 

Histogram

A histogram looks like a bar chart, but here the bars are placed directly next to each other without gaps. This is because the intervals cover a continuous range of numbers.

Histograms are especially used when the observations are measured in numbers that can vary continuously, such as height, weight or time.

 

In a histogram you can quickly see the distribution of the data and assess whether it is symmetric, skewed or has special patterns.