To understand the results of a scatter plot, especially when looking at regression and correlation, follow these simple steps:
-
Identify the Variables:
- Start by naming your independent variable (this is usually X) and your dependent variable (this is usually Y).
-
Look for Patterns:
- Check the scatter plot for any patterns:
- Positive Correlation: If the points go up as you move from left to right, this shows a positive correlation.
- Negative Correlation: If the points go down from left to right, this shows a negative correlation.
- No Correlation: If the points are spread out randomly, there’s very little or no correlation.
-
Calculate the Correlation Coefficient (r):
- This number helps you see how strong the relationship is between the two variables.
- The value of r can be between -1 and 1:
- r≈1: This means a strong positive correlation.
- r≈−1: This means a strong negative correlation.
- r≈0: This means there is little to no linear correlation.
-
Perform Linear Regression:
- Use a method called least squares to find the best-fitting line.
- This line can be represented by the equation Y=a+bX, where b is the slope and a is where the line crosses the Y-axis.
-
Check the Results:
- Look at the residuals (the differences between the observed and predicted values) and find R2 (which tells you how well your model works).
- A higher R2 value, which is closer to 1, shows that your model explains a big part of the change in Y.
Following these steps will help you make sense of what the scatter plot is telling you!