Step by step
The question
Question: draw a histogram of 150, 162, 171, 158, 166, 153, 175, 168, 161 and 164, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 150 and the biggest is 175.
In classes of 10: 150 to 159, 160 to 169 and 170 to 179.
2 Make a frequency table
A frequency table first: one row for each class.
150 is in 150 to 159: a mark there, and we cross out 150.
162 is in 160 to 169.
And so on for every number.
We count the marks: 3, 5 and 2.
3 Draw the bars
Along the bottom: the numbers, from 150 to 180.
Up the side: how many.
150 to 159: 3 numbers.
The bar covers 150 to 160 and goes up to 3.
160 to 169: 5.
170 to 179: 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 160 to 169.
It reaches 5.
So the class with the most is 160-169, with 5 numbers.
5 Check
Let's check: all the bars together are 3 plus 5 plus 2, which is 10.
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.