Step by step
The question
Question: draw a histogram of 52, 67, 71, 58, 63, 75, 69, 81, 66, 72, 64 and 77, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 52 and the biggest is 81.
In classes of 10: 50 to 59, 60 to 69, 70 to 79 and 80 to 89.
2 Make a frequency table
A frequency table first: one row for each class.
52 is in 50 to 59: a mark there, and we cross out 52.
67 is in 60 to 69.
And so on for every number.
We count the marks: 2, 5, 4 and 1.
3 Draw the bars
Along the bottom: the numbers, from 50 to 90.
Up the side: how many.
50 to 59: 2 numbers.
The bar covers 50 to 60 and goes up to 2.
60 to 69: 5.
70 to 79: 4.
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 60 to 69.
It reaches 5.
So the class with the most is 60-69, with 5 numbers.
5 Check
Let's check: all the bars together are 2 plus 5 plus 4 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.