Model Evaluation - lesson 2 | HackIndia Skills

Model Evaluation - lesson 2 | HackIndia Skills | HackIndia

Example

Small example

Here is a confusion matrix for 100 transactions. Rows are actual labels. Columns are predicted labels.

The model catches 12 fraud cases, misses 8 fraud cases, wrongly blocks 5 normal transactions, and allows 75 normal transactions.

                 Predicted normal   Predicted fraud
Actual normal          75                 5
Actual fraud            8                12

Example

Make one in Python

Use this with your saved validation labels and predictions. It prints the label order so you do not guess.

For a college project, put the matrix screenshot or table in your README or demo slides.

from sklearn.metrics import confusion_matrix, ConfusionMatrixDisplay
import matplotlib.pyplot as plt

# Example labels: 1 = fraud, 0 = normal
y_true = [0, 0, 0, 0, 1, 1, 1, 1, 1, 0]
y_pred = [0, 0, 1, 0, 1, 0, 1, 0, 1, 0]

labels = [0, 1]
cm = confusion_matrix(y_true, y_pred, labels=labels)
print("Label order:", labels)
print(cm)

# Rows are actual. Columns are predicted.
disp = ConfusionMatrixDisplay(confusion_matrix=cm, display_labels=["normal", "fraud"])
disp.plot(values_format="d")
plt.title("Confusion matrix on validation set")
plt.savefig("confusion_matrix.png", bbox_inches="tight")

Tip

Use AI carefully

You can ask ChatGPT or Gemini to explain your confusion matrix in simple words. Paste the matrix, label order, and what positive means.

Check the answer yourself. Make sure it does not invent precision, recall, business impact, or dataset details you did not provide.

Prompt:
Explain this confusion matrix for my hackathon README.
Task: UPI fraud detection.
Positive class: fraud.
Rows are actual labels. Columns are predicted labels.
Labels: [normal, fraud]
Matrix:
[[75, 5],
 [8, 12]]
Keep it honest and mention the main mistake.

Read a confusion matrix

The one idea

The four cells

Small example

Common reading mistake

Read it safely

Make one in Python

Use AI carefully

Do this now

Quick check