Step by step
The question
Question: draw a histogram of 31, 45, 38, 52, 47, 33, 41, 49, 36, 44 and 58, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 31 and the biggest is 58.
In classes of 10: 30 to 39, 40 to 49 and 50 to 59.
2 Make a frequency table
A frequency table first: one row for each class.
31 is in 30 to 39: a mark there, and we cross out 31.
45 is in 40 to 49.
And so on for every number.
We count the marks: 4, 5 and 2.
3 Draw the bars
Along the bottom: the numbers, from 30 to 60.
Up the side: how many.
30 to 39: 4 numbers.
The bar covers 30 to 40 and goes up to 4.
40 to 49: 5.
50 to 59: 2.
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 40 to 49.
It reaches 5.
So the class with the most is 40-49, with 5 numbers.
5 Check
Let's check: all the bars together are 4 plus 5 plus 2, which is 11.
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.