Step by step
The question
Question: draw a histogram of 47, 52, 38, 61, 55, 43, 58, 49, 66, 51, 45, 57, 53 and 40, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 38 and the biggest is 66.
In classes of 10: 30 to 39, 40 to 49, 50 to 59 and 60 to 69.
2 Make a frequency table
A frequency table first: one row for each class.
47 is in 40 to 49: a mark there, and we cross out 47.
52 is in 50 to 59.
And so on for every number.
We count the marks: 1, 5, 6 and 2.
3 Draw the bars
Along the bottom: the numbers, from 30 to 70.
Up the side: how many.
30 to 39: 1 number.
The bar covers 30 to 40 and goes up to 1.
40 to 49: 5.
50 to 59: 6.
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 50 to 59.
It reaches 6.
So the class with the most is 50-59, with 6 numbers.
5 Check
Let's check: all the bars together are 1 plus 5 plus 6 plus 2, which is 14.
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.