Step by step
The question
Question: draw a scatter plot of (1, 3), (2, 7), (3, 4), (4, 9), (5, 5), (6, 10), (7, 8).
What is the correlation?
Correlation tells if y goes up or down as x goes up, and how closely.
1 Draw the axes
x goes along the bottom.
y goes up the side.
2 Plot the points
(1, 3): across to 1, then up to 3.
(2, 7): across 2, up 7.
And so on, one dot for each point.
3 Find the direction
We draw a line along the points.
It goes uphill: from bottom left to top right.
As x goes up, y goes up too.
That is a positive correlation.
4 Find the strength
Two lines hold all the points.
The band is wide: the points are spread out from the line.
So the correlation is weak.
Careful!
A correlation shows that two things move together.
It does not prove that one causes the other.
So the answer: weak positive correlation.
5 Check
Let's check with numbers.
The 3 points on the left have a mean y of about 4.7.
The 3 on the right: about 7.7.
The right is higher: it goes up.
So it is right!
Let's look back.
First: draw the axes.
Then: plot the points.
Then: find the direction.
Then: find the strength.
Last: check.