Step by step
The question
Question: draw a histogram of 3, 8, 14, 21, 9, 16, 5, 12, 18, 11, 7, 15 and 6, in classes of 5.
Which class has the most?
1 Make the classes
The smallest number is 3 and the biggest is 21.
In classes of 5: 0 to 4, 5 to 9, 10 to 14, 15 to 19 and 20 to 24.
2 Make a frequency table
A frequency table first: one row for each class.
3 is in 0 to 4: a mark there, and we cross out 3.
8 is in 5 to 9.
And so on for every number.
We count the marks: 1, 5, 3, 3 and 1.
3 Draw the bars
Along the bottom: the numbers, from 0 to 25.
Up the side: how many.
0 to 4: 1 number.
The bar covers 0 to 5 and goes up to 1.
5 to 9: 5.
10 to 14: 3.
Careful!
The bars touch.
The numbers go on with no gaps, like a number line.
A bar chart has gaps; a histogram does not.
4 Read the histogram
The tallest bar is 5 to 9.
It reaches 5.
So the class with the most is 5-9, with 5 numbers.
5 Check
Let's check: all the bars together are 1 plus 5 plus 3 plus 3 plus 1, which is 13.
That is every number in the list.
So it is right!
Let's look back.
First: make the classes.
Then: make a frequency table.
Then: draw the bars.
Then: read the histogram.
Last: check.