Is Your Regression Model Misleading You? The Truth Behind QQ Plots!

QQ Plot: Uses, Benefits & Interpreting

1. What's a QQ Plot?

   • A QQ plot is a graph that helps us see if our data follows a particular pattern, like a normal distribution. It's like a detective tool for statisticians.

2. How it Works:

   • We use QQ plots to check if our data is similar to a known pattern (like normal distribution) or if two sets of data are similar.

3. Drawing the Graph:

   • Imagine two lines on a graph. One line represents our data, and the other represents the expected pattern. If our data perfectly matches the pattern, the dots would fall on a line at a 45-degree angle.

4. Understanding the Dots:

   • When the dots mostly follow the 45-degree line, our data is similar to the expected pattern. If the dots stray, there might be something different about our data.

5. Signs of Differences:

   • The graph can show us if our data has unusual shapes. For example, if the dots form a curve, it means our data might not be quite normal.

6. Why QQ Plots Are Useful:

   • QQ plots are better than other methods, like histograms or tests, because they give us a clear picture. They're like a reliable detective helping us understand our data.

7. Comparison with Tests:

   • Sometimes, other tests can make mistakes, especially with lots of data. QQ plots help us see the real story, even when the tests get confused.

8. Real-Life Examples:

   • The article shows us pictures to help understand how QQ plots work. It's like looking at evidence to solve a mystery about our data.
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   • Note: In Regression Analysis, QQ plot is great way to determine whether residual follows normal distribution ( which is important assumption of Linear regression model)
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   • Example : In the below all the blue dots follow straight line. Hence Normal
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     Example : In Below graph, all the blue dots follow straight a curve (approx. S shape curve). Hence Not Normal.
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9. Final Thoughts: QQ plots are like superheroes for statisticians, helping us understand if our data is behaving as we expect. They make complex things simpler and clearer.

Next Article: Is Your Regression Misbehaving? Unraveling the Mystery of Non-Normal Residuals!

Reference (image source) : https://statisticsbyjim.com/graphs/qq-plot/

https://en.wikipedia.org/wiki/Q%E2%80%93Q_plot