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    Dropout & Batch Normalization

    AI · Advanced

    Definition

    Dropout randomly disables neurons during training; batch norm normalizes layer inputs per mini-batch.

    Both improve generalization and training stability.

    Diagram

    layer→ BN→ ReLU→ Dropout

    Flowchart

    Forward passDropout masks neurons (training only)BatchNorm normalizes to mean 0, std 1Scale and shift

    Example: Normalize a batch

    x = [2, 4, 6]
    m = sum(x) / 3
    s = (sum((v - m) ** 2 for v in x) / 3) ** 0.5
    print([round((v - m) / s, 2) for v in x])

    Output: [-1.22, 0.0, 1.22]

    Key points

    • Dropout is off at inference
    • Typical dropout rate 0.2–0.5

    Interview questions

    Why is dropout off during testing?

    Predictions should be deterministic and use the full network.

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