🧠 Adaptive Diagnostic Engine

A 1-Dimension Adaptive Testing system that dynamically selects GRE-style questions based on a student's real-time performance using Item Response Theory (IRT), then generates a personalized AI-powered study plan via Gemini 1.5 Flash.

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🚀 Live Demo

Deployed on Render: https://adaptive-engine.onrender.com
Interactive API Docs: https://adaptive-engine.onrender.com/docs

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⚙️ Tech Stack

Layer	Technology
Backend	FastAPI (Python)
Database	MongoDB Atlas
Adaptive Algorithm	1PL Item Response Theory
AI Study Plan	Google Gemini 1.5 Flash
Deployment	Render (free tier)

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📁 Project Structure

adaptive-engine/
├── app/
│   ├── main.py              # FastAPI app + CORS
│   ├── routes/
│   │   └── adaptive.py      # All API endpoints
│   ├── models/
│   │   └── schemas.py       # Pydantic models
│   ├── db/
│   │   └── connection.py    # MongoDB client
│   ├── algorithm/
│   │   └── irt.py           # IRT math (pure Python, no side effects)
│   └── ai/
│       └── study_plan.py    # Gemini 1.5 Flash integration
├── seed/
│   └── seed_questions.py    # Seeds 25 GRE questions
├── .env.example
├── requirements.txt
└── README.md

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🛠️ Local Setup

1. Clone the repo

git clone https://github.com/YOUR_USERNAME/adaptive-engine.git
cd adaptive-engine

2. Create a virtual environment

python -m venv venv
source venv/bin/activate        # Windows: venv\Scripts\activate

3. Install dependencies

pip install -r requirements.txt

4. Configure environment variables

cp .env.example .env

Edit .env:

MONGODB_URI=mongodb+srv://user:password@cluster0.xxxxx.mongodb.net/adaptive_engine
GEMINI_API_KEY=AIzaSy...your_key_here

5. Seed the database

python seed/seed_questions.py

6. Run the server

uvicorn app.main:app --reload

Visit http://localhost:8000/docs for the interactive Swagger UI.

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📡 API Documentation

POST /api/start-session

Creates a new student session at baseline ability 0.5.

Response:

{
  "session_id": "uuid-here",
  "message": "Session started. Call GET /api/next-question?session_id=<id> to begin."
}

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GET /api/next-question?session_id=<id>

Returns the next adaptive question, selected by IRT to be closest in difficulty to the student's current ability score.

Response:

{
  "session_id": "...",
  "question_number": 1,
  "question_id": "ALG001",
  "text": "If 2x + 4 = 10, what is x?",
  "options": {"A": "2", "B": "3", "C": "4", "D": "5"},
  "topic": "Algebra",
  "difficulty": 0.1
}

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POST /api/submit-answer

Submits the student's answer. Updates ability score using IRT.

Request body:

{
  "session_id": "uuid-here",
  "question_id": "ALG001",
  "selected_answer": "B"
}

Response:

{
  "is_correct": true,
  "correct_answer": "B",
  "updated_ability_score": 0.55,
  "questions_answered": 1,
  "is_complete": false,
  "message": "Correct! Next question will be slightly harder."
}

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GET /api/study-plan?session_id=<id>

Available after all 10 questions are answered. Calls Gemini 1.5 Flash to generate a personalized 3-step study plan.

Response:

{
  "session_id": "...",
  "ability_score": 0.63,
  "total_questions": 10,
  "correct_count": 6,
  "weak_topics": ["Vocabulary", "Data Analysis"],
  "study_plan": "## Your 3-Step Study Plan\n\n**Step 1: ...**"
}

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GET /api/session-status?session_id=<id>

Debug endpoint to inspect full session state including all answers.

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🧮 Adaptive Algorithm Logic

The system uses the 1-Parameter Logistic (1PL) IRT model.

Probability of Correct Response

P(correct | θ, b) = 1 / (1 + e^-(θ - b))

• θ (theta): Student ability score [0.1 – 1.0], starts at 0.5
• b: Question difficulty [0.1 – 1.0]

Ability Score Update

After each answer, ability is updated using gradient ascent on the log-likelihood:

θ_new = θ_old + α × (actual - P)

• α = 0.1 (learning rate — conservative for stability)
• actual = 1 if correct, 0 if incorrect

Why This Works

• When a student answers correctly, actual (1) > P, so θ increases
• When incorrect, actual (0) < P, so θ decreases
• The magnitude of change is naturally smaller when the result is "expected" (e.g., a strong student getting an easy question right barely increases their score)
• This is mathematically superior to naive +0.1/-0.1 jumps

Question Selection

The next question is selected whose difficulty b is closest to the student's current θ. This maximises measurement information per question.

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🤖 AI Log: How AI Tools Were Used

Claude (Anthropic): Used extensively for:

• Architecting the clean modular project structure
• Implementing the IRT algorithm with proper mathematical grounding
• Writing the Gemini prompt to elicit structured, data-driven study plans
• Generating all 25 GRE-style seed questions with calibrated difficulty scores
• Writing the comprehensive README

Challenges AI couldn't solve:

• Calibrating question difficulty scores required domain judgment — AI suggested values that needed manual review to ensure they felt authentically GRE-appropriate
• MongoDB Atlas network access configuration (IP whitelisting for Render) required manual setup in the Atlas dashboard — AI could explain steps but couldn't perform them

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🌐 Deployment on Render

1. Push repo to GitHub
2. Go to render.com → New Web Service
3. Connect your GitHub repo
4. Build Command: pip install -r requirements.txt
5. Start Command: uvicorn app.main:app --host 0.0.0.0 --port $PORT
6. Add environment variables: MONGODB_URI, GEMINI_API_KEY
7. Deploy → get your *.onrender.com URL

Note: Free tier spins down after 15 min inactivity. First request after idle has a ~30s cold start.