Step by step
The question
Question: draw a histogram of 61, 74, 68, 85, 79, 72, 90, 77, 83, 70, 66, 88 and 75, in classes of 10.
Which class has the most?
1 Make the classes
The smallest number is 61 and the biggest is 90.
In classes of 10: 60 to 69, 70 to 79, 80 to 89 and 90 to 99.
2 Make a frequency table
A frequency table first: one row for each class.
61 is in 60 to 69: a mark there, and we cross out 61.
74 is in 70 to 79.
And so on for every number.
We count the marks: 3, 6, 3 and 1.
3 Draw the bars
Along the bottom: the numbers, from 60 to 100.
Up the side: how many.
60 to 69: 3 numbers.
The bar covers 60 to 70 and goes up to 3.
70 to 79: 6.
80 to 89: 3.
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 70 to 79.
It reaches 6.
So the class with the most is 70-79, with 6 numbers.
5 Check
Let's check: all the bars together are 3 plus 6 plus 3 plus 1, which is 13.
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.