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Scatterplots and correlation review

A scatterplot is a type of data display that shows the relationship between two numerical variables. Each member of the dataset gets plotted as a point whose x-y coordinates relates to its values for the two variables.

What is a scatterplot?

A scatterplot is a type of data display that shows the relationship between two numerical variables. Each member of the dataset gets plotted as a point whose (x,y) coordinates relates to its values for the two variables.
For example, here is a scatterplot that shows the shoe sizes and quiz scores for students in a class:
A graph plots Score on the y-axis, versus Shoe size on the x-axis. Approximately 2 dozen points are scattered sporadically between x = 5.5 and x = 11, and between y = 52 and y = 87. All values estimated.
Each data point is a student whose x-coordinate gives their shoe size and y-coordinate gives their quiz score.
Want to learn more about constructing scatterplots? Check out this video.

What is correlation?

We often see patterns or relationships in scatterplots.
When the y variable tends to increase as the x variable increases, we say there is a positive correlation between the variables.
Positive correlation
A scatterplot plots points x y axis. Approximately 2 dozen points are rise diagonally in a relatively narrow patterm between (1 half, 1 half) and (9, 7 and 1 half). All values estimated.
When the y variable tends to decrease as the x variable increases, we say there is a negative correlation between the variables.
Negative correlation
A scatterplot plots points x y axis. Approximately 2 dozen points are fall diagonally in a relatively narrow patterm between (1 half, 6) and (8, 2). All values estimated.
When there is no clear relationship between the two variables, we say there is no correlation between the two variables.
No correlation
A scatterplot plots points x y axis. Approximately 2 dozen points are scattered sporadically between x = 1 half and x = 9, and between y = 2 and y = 9. All values estimated.
Want to learn more about types of correlation? Check out this video.

Practice

problem 1
The graph shown below shows the relationship between the age of drivers and the number of car accidents per 100 drivers in the year 2009.
What is the best description of this relationship?
Choose 1 answer:
The scatterplot falls diagonally in a relatively narrow pattern.

Want to practice more problems like these? Check out this exercise on positive and negative correlations.

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