Step by step
The question
Question: draw a histogram of 1, 4, 6, 2, 9, 3, 7, 5, 4, 8, 3 and 2, in classes of 3.
Which class has the most?
1 Make the classes
The smallest number is 1 and the biggest is 9.
In classes of 3: 0 to 2, 3 to 5, 6 to 8 and 9 to 11.
2 Make a frequency table
A frequency table first: one row for each class.
1 is in 0 to 2: a mark there, and we cross out 1.
4 is in 3 to 5.
And so on for every number.
We count the marks: 3, 5, 3 and 1.
3 Draw the bars
Along the bottom: the numbers, from 0 to 12.
Up the side: how many.
0 to 2: 3 numbers.
The bar covers 0 to 3 and goes up to 3.
3 to 5: 5.
6 to 8: 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 3 to 5.
It reaches 5.
So the class with the most is 3-5, with 5 numbers.
5 Check
Let's check: all the bars together are 3 plus 5 plus 3 plus 1, which is 12.
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.