Step by step
The question
Question: draw a histogram of 140, 152, 147, 161, 155, 149, 158, 143, 166, 151 and 157, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 140 and the biggest is 166.
In classes of 10: 140 to 149, 150 to 159 and 160 to 169.
2 Make a frequency table
A frequency table first: one row for each class.
140 is in 140 to 149: a mark there, and we cross out 140.
152 is in 150 to 159.
And so on for every number.
We count the marks: 4, 5 and 2.
3 Draw the bars
Along the bottom: the numbers, from 140 to 170.
Up the side: how many.
140 to 149: 4 numbers.
The bar covers 140 to 150 and goes up to 4.
150 to 159: 5.
160 to 169: 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 150 to 159.
It reaches 5.
So the class with the most is 150-159, 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.