Step by step
The question
Question: draw a histogram of 3, 7, 12, 5, 14, 9, 11, 2, 8, 6, 10 and 13, in classes of 5.
Which class has the most?
1 Make the classes
The smallest number is 2 and the biggest is 14.
In classes of 5: 0 to 4, 5 to 9 and 10 to 14.
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.
7 is in 5 to 9.
And so on for every number.
We count the marks: 2, 5 and 5.
3 Draw the bars
Along the bottom: the numbers, from 0 to 15.
Up the side: how many.
0 to 4: 2 numbers.
The bar covers 0 to 5 and goes up to 2.
5 to 9: 5.
10 to 14: 5.
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 2 plus 5 plus 5, 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.