Scatter Plots & Correlation 📊

What Is a Scatter Plot?

A scatter plot shows the relationship between two numerical variables. Each data point is a dot — its position on the x-axis represents one variable, its y position represents another.

import matplotlib.pyplot as plt

hours  = [1, 2, 3, 4, 5, 6, 7, 8]
scores = [55, 58, 65, 70, 72, 80, 82, 88]

plt.scatter(hours, scores, color="steelblue")
plt.xlabel("Hours Studied")
plt.ylabel("Test Score")
plt.title("Study Hours vs. Score")
plt.show()

Types of Correlation

• Positive correlation: as x increases, y increases (e.g., study hours → scores).
• Negative correlation: as x increases, y decreases (e.g., absences → grades).
• No correlation: dots are scattered randomly — no pattern.

Spotting Outliers

An outlier is a point far from the main cluster. It might be a data entry error, or it might be a genuinely unusual case worth investigating.