Step by step
The question
Question: describe the data 3, 4, 4, 5, 7, 7, 7: its center, its spread and its shape.
1 Draw a dot plot
A number line from 3 to 7.
One dot for each number.
3 first.
And so on.
2 Find the center
There are 7 numbers.
We count in from both ends to the middle one: number 4.
On the dot plot, that is 5.
The median is the center.
Careful!
The tallest stack is 7.
But the center is the middle value, 5.
3 Find the spread
The spread: biggest minus smallest.
7 minus 3 is 4.
4 Describe the shape
The tallest stack, the peak, is at 7.
One peak, at 7.
No dots at 6: a gap.
Most dots are on the right.
A few spread out to the left: a tail to the left.
5 Check
Let's check: we count the dots.
7 dots for 7 numbers.
Every number is crossed out.
So the dot plot is right, and so is the answer!
Let's look back.
First: draw a dot plot.
Then: find the center.
Then: find the spread.
Then: describe the shape.
Last: check.