Step by step
The question
Question: describe the data 2, 6, 6, 7, 7, 7, 8: its center, its spread and its shape.
2, 6, 6, 7, 7, 7, 8
1 Draw a dot plot
A number line from 2 to 8.
One dot for each number.
2 first.
And so on.
2 Find the center
There are 7 numbers.
We count in from both ends to the middle one: number 4.
= 7 numbers: middle = number 4
On the dot plot, that is 7.
The median is the center.
= center: median = 7
3 Find the spread
The spread: biggest minus smallest.
8 minus 2 is 6.
= spread: range = 8 − 2 = 6
4 Describe the shape
The tallest stack, the peak, is at 7.
One peak, at 7.
No dots at 3, 4 and 5: a gap.
Most dots are on the right.
A few spread out to the left: a tail to the left.
= shape: peak at 7, gap at 3, 4 and 5, 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!
7 dots, 7 numbers
Let's look back.
First: draw a dot plot.
Then: find the center.
Then: find the spread.
Then: describe the shape.
Last: check.
Answer
= shape: peak at 7, gap at 3, 4 and 5, tail to the left