Data Science Portfolio - Kaggle Datasets & AI Projects | Artificial Intelligence
🔹 DATA SCIENCE – INTERVIEW REVISION SHEET
1️⃣ What is Data Science?
> “Data science is the process of using data, statistics, and machine learning to extract insights and build predictive or decision-making models.”
Difference from Data Analytics:
• Data Analytics → past present (what/why)
• Data Science → future automation (what will happen)
2️⃣ Data Science Lifecycle (Very Important)
1. Business problem understanding
2. Data collection
3. Data cleaning preprocessing
4. Exploratory Data Analysis (EDA)
5. Feature engineering
6. Model building
7. Model evaluation
8. Deployment monitoring
Interview line:
> “I always start from business understanding, not the model.”
3️⃣ Data Types
• Structured → tables, SQL
• Semi-structured → JSON, logs
• Unstructured → text, images
4️⃣ Statistics You MUST Know
• Central tendency: Mean, Median (use when outliers exist)
• Spread: Variance, Standard deviation
• Correlation ≠ causation
• Normal distribution
• Skewness (income → right skewed)
5️⃣ Data Cleaning Preprocessing
Steps you should say in interviews:
1. Handle missing values
2. Remove duplicates
3. Treat outliers
4. Encode categorical variables
5. Scale numerical data
Scaling:
• Min-Max → bounded range
• Standardization → normal distribution
6️⃣ Feature Engineering (Interview Favorite)
> “Feature engineering is creating meaningful input variables that improve model performance.”
Examples:
• Extract month from date
• Create customer lifetime value
• Binning age groups
7️⃣ Machine Learning Basics
• Supervised learning: Regression, Classification
• Unsupervised learning: Clustering, Dimensionality reduction
8️⃣ Common Algorithms (Know WHEN to use)
• Regression: Linear regression → continuous output
• Classification: Logistic regression, Decision tree, Random forest, SVM
• Unsupervised: K-Means → segmentation, PCA → dimensionality reduction
9️⃣ Overfitting vs Underfitting
• Overfitting → model memorizes training data
• Underfitting → model too simple
Fixes:
• Regulari
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