# Evaluating Correlation

#### CourseDescription

Correlation is one of the most common, and widely-used, statistical methods when dealing with various data sets. Correlation analysis helps in understanding the relationship between objects or variables. This video introduces the basic concepts of correlation, highlighting its significance in data analysis.

What You'll Learn

Correlation in data analysis

Importance of correlation in data science

Another very common one is a correlation.

Correlation measures, essentially, the linear relationship between the objects. It tells us if objects p and q move together, is kind of the way to think about it. So, what we do with this is standardize each of the objects’ attributes, and then we take their dot product. It gives us a value between 1 and negative 1. So, it’s not exactly a standard similarity measurement that we can square it, and then it becomes between 0 and 1 and becomes a standard similarity measurement. That’s sometimes called the coefficient of determination. Sorry. R is the coefficient of determination. R squared is the correlation. I don’t remember my statistics classes well enough. I apologize. The two tend to get used in data science very interchangeably.

So here, for those of you who haven’t had that much statistics or who don’t remember, is a visual example of our correlations. When the correlation is negative 1, which is the lowest possible value, we have a very linear relationship. As one object goes up, the other comes down, whatever up and down happens to mean in this context. And with a correlation of 1, we have the objects going up together or coming down together. And as we get to correlations that are closer to 0, we can see that this data clearly has a very little relationship. Whereas if we get closer to 1 and negative 1, we see a sharper and sharper linear relationship between the two.

Correlation is one of the metrics that we use to evaluate regression models. So we’ll talk about it more in that context. But I just wanted to make sure we introduced it so people had heard the word if you haven’t had much of a statistics background, or it’s been a while.

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