Scenario
You are interviewing for a Data Scientist role and are asked to design a predictive model for a key product metric in a consumer app (e.g., predicting whether a user will perform an action such as sending a message or completing a sign-up) during a statistics/ML round.
Task
Walk through how you would build a model for this business case, from defining the target and features through evaluation and iteration. Specifically:
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Define the prediction problem, target variable, and feature space.
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Describe data preprocessing and how you would set up train/validation/test splits (including time-based considerations to avoid leakage).
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Write down the mathematical form of the logistic function and explain why it is appropriate for binary classification problems.
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Explain what is "random" in Random Forests and why that randomness improves model performance.
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Outline how you would evaluate the model and iterate.
Notes
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Include variable definitions, data preprocessing steps, and relevant evaluation metrics.
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Logistic equation:
σ(z)=1+e−z1
.
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In Random Forests, discuss bootstrapped samples and random feature subsets.