Understand how to calculate the correlation coefficient in PostgreSQL.
- [Instructor] We can calculate…a measure of correlation using a formula called…the Pearson's correlation coefficient.…The formula calculates a number between…negative one and positive one.…A negative one means the variables…are highly negatively correlated.…A positive one means they are highly positively correlated.…A zero means they're not correlated at all.…The formula for Pearson's correlation coefficient…is based on the standard deviation…of the distribution of variables…and a measure called the covariance…between the two variables.…
The details of the formula…are beyond the scope of this lesson,…but if you are interested,…you can find the details at Wikipedia…on the page about Pearson's correlation coefficient.…For our purposes, we shall use a SQL function,…CORR, or C-O-R-R, in PostgreSQL.…It takes two values, such as columns in a table,…and returns a value between negative one and one.…Let's imagine we have a product sales table…with the number of units sold and the total revenue.…
We can calculate the correlation…
Author
Dan Sullivan
Released
6/7/2018- Exploratory data analysis vs. hypothesis-driven statistical analysis
- Performing data quality checks
- Calculating quartiles
- Using box plot to understand the distribution of values
- Using histograms to understand the frequency of values
- Using chi square to understand the correlation between values
Skill Level Beginner
Duration
Views
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Introduction
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Welcome54s
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1. Introduction to Exploratory Data Analysis
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Why explore data?1m 28s
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2. Data Quality Checks
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Why check data?2m 56s
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Types of quality checks2m 53s
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Imputing missing values2m 53s
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3. Calculating Quartiles
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Ordering and counting2m 22s
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Calculating quartiles1m 51s
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Introduction to box plots2m 28s
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4. Histograms
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Introduction to histograms1m 50s
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Partitioning data2m 5s
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Calculating histograms1m 12s
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5. Checking Correlation between Attributes
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Introduction to correlation1m 41s
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Conclusion
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Next steps1m 9s
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Video: Calculating correlation with SQL