Linear Data

We can visualize data involving two variables as scatterplots​

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​A scatterplot is a graph of points, when we graph the data points we may be able to recognize a pattern.

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​The scatterplot on the right appears to have a linear relationship.

Correlation is a measure of strength and direction of this relationship. Lets look at the direction.

​It is similar to slope. If the datapoints and graph is increasing, the correlation is positive. If the datapoints and graph is decreasing, the correlation is negative. At times the points appear neither decreasing or incresing overall. In this case there is no correlation

We can sometimes reasonable predict whether or not a situation has positive, negative, or no correlation without any data or graph.

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​For example: the weight of a car and the number of miles per gallon

​ These two would probably have a negative correlation. This is beacuse a heavier car usually gets less miles to the gallon.

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​For example: the amount of time studying and the grade on a science exam

​ These two would probably have a positive correlation. The more time a student puts into studying, the higher their grade will be

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​ This is not always true, but it is a reasonable prediction.

​Now lets talk about correlation strength.

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​We represent the strength of the correlation with a number between -1 and 1.

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​The closer to 1 or -1, the stronger the correlation