Step by step
The question
Question: describe the data 1, 2, 2, 2, 3, 6, 7, 7, 7, 8, 8: its center, its spread and its shape.
1, 2, 2, 2, 3, 6, 7, 7, 7, 8, 8
1 Draw a dot plot
A number line from 1 to 8.
One dot for each number.
1 first.
And so on.
2 Find the center
There are 11 numbers.
We count in from both ends to the middle one: number 6.
= 11 numbers: middle = number 6
On the dot plot, that is 6.
The median is the center.
= center: median = 6
3 Find the spread
The spread: biggest minus smallest.
8 minus 1 is 7.
= spread: range = 8 − 1 = 7
4 Describe the shape
2 has 3 dots.
7 has 3 dots.
The peaks are at 2 and 7.
No dots at 4 and 5: a gap.
The dots make two groups, with the gap between them: two clusters.
= shape: peak at 2 and 7, gap at 4 and 5, two clusters
5 Check
Let's check: we count the dots.
11 dots for 11 numbers.
Every number is crossed out.
So the dot plot is right, and so is the answer!
11 dots, 11 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 2 and 7, gap at 4 and 5, two clusters