Scatter plots


Scatter plots are used to show relationship between two sets of data by writing them as ordered pairs

To illustrate, let us pretend that you have a business that sells notebooks

Day 1, you sell 10 notebooks

Day 1, you sell 10 notebooks

Day 2, you sell 5 notebooks

Day 3, you sell 15 notebooks

Day 4, you sell 10 notebooks

Day5 , you sell 20 notebooks

Day 6, you sell 15 notebooks

Day 7, you sell 30 notebooks

Day 8, you sell 15 notebooks

Day 9, you sell 25 notebooks

Day 10, you sell 15 notebooks

You can display this situation with ordered pairs as shown below:

(1,10), (2,5), (3,15), (4,10), (5,20), (6,15), (7,30), (8,15), (9, 25), and (10, 15)

Then we can put the ordered pairs on the coordinate system. The resulting graph is called a scatter plot or scatter graph.

Notice how the points are scattered around and everything is located in the first quadrant

Scatter plot


Two sets of data can form 3 types of relationships

When y increases as x increases, the two sets of data have a positive correlation

Basically, when you closely examine the graph, you will see that the graph has a tendency to go upward

Example

Positive correlation
When y decreases as x increases, the two sets of data have a negative correlation

Basically, when you closely examine the graph, you will see that the graph has a tendency to go downward

Example

Negative correlation
When x and y are not related, we say that the two sets of data have no correlation

Example

No correlation


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