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Shiva Charan
Shiva Charan

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Interpretability & Explainability

Big picture first

Interpretability and Explainability both answer one question:

Can humans understand why an AI made a decision?

But they answer it in different ways.


1️⃣ Interpretability in AI

What it means (simple words)

Interpretability = the model is understandable by design.

You can look at the model itself and immediately see how inputs affect outputs.

No extra tools.
No post-processing.
No guessing.


Example

Linear / Logistic Regression

If a model says:

Final score = (0.8 × Experience) + (1.2 × Education) − (0.5 × Age)
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You instantly know:

  • Education matters more than experience
  • Age slightly reduces the score

That’s interpretability.


Real-world example

Loan approval with Logistic Regression

Feature Weight Meaning
Income +2.5 Higher income strongly increases approval
Debt −3.0 More debt strongly decreases approval
Credit history +1.8 Good history helps

You do not need an explanation system.
The model explains itself.


Key idea

If you can understand the model just by reading it, it is interpretable.


2️⃣ Explainability in AI

What it means (simple words)

Explainability = the model is complex, but we add tools to explain its decisions.

The model itself is a black box.
We explain it after it makes predictions.


Example

Deep Neural Network for medical diagnosis

  • Input: X-ray image
  • Output: “Pneumonia: 92% probability”

You cannot read the model weights and understand why.

So you use explainability tools like:

  • Highlighting image regions
  • Feature importance charts
  • Decision approximations

Real-world example

Credit card fraud detection using Deep Learning

The model says:

“This transaction is fraud”

Explainability tools then say:

  • Unusual location
  • Amount higher than normal
  • Time of transaction abnormal

The explanation is added on top, not built in.


Key idea

The model is powerful but opaque, so we explain its behavior externally.


Visual intuition

Left side: Simple glass box
Right side: Black box with explanation layer


3️⃣ Side-by-side comparison

Aspect Interpretability Explainability
Model type Simple by design Complex black-box
Human understanding Direct Indirect
Extra tools needed ❌ No ✅ Yes
Examples Linear regression, decision trees Neural networks, ensemble models
Accuracy Usually lower Usually higher
Transparency High Medium

4️⃣ Why do these concepts exist?

1️⃣ Trust

If a doctor, bank, or judge uses AI, they will ask:

“Why did it say that?”

Blind trust is unacceptable.


2️⃣ Regulation and compliance

Many laws require:

  • Decision justification
  • Bias detection
  • Right to explanation

You cannot say:

“The neural network felt like it.”


3️⃣ Debugging models

If a model fails:

  • Interpretability helps you fix the model
  • Explainability helps you understand failures

4️⃣ Bias and fairness

Without understanding decisions:

  • Models can discriminate
  • Errors go unnoticed
  • Legal risk increases

5️⃣ Safety-critical systems

In healthcare, finance, self-driving cars:

  • Wrong decisions kill people or cost millions
  • Explanations are not optional

5️⃣ Rule of thumb

Remember this and you will never get confused:

Interpretability is built-in clarity
Explainability is added clarity

Or even shorter:

Simple models are interpretable
Complex models must be explainable


6️⃣ One-line example to lock it in

  • Logistic Regression approves a loan because income weight is high → Interpretability
  • Neural Network approves a loan and SHAP explains income mattered most → Explainability

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