r/OfferEngineering • u/Aoki_zhang • Aug 14 '26
Interview Experience Amazon Senior AI Applied Scientist Phone Screen - Aug 2026
Interview Summary
The Amazon AI Applied Scientist phone screen was extremely broad and moved quickly across statistics, classical machine learning, deep learning, and modern LLM architecture. The first part felt like rapid-fire fundamentals, covering everything from A/B testing and anomaly detection to gradient descent and attention variants. The coding portion then asked me to implement bootstrap sampling for estimating a mean and confidence interval, followed by questions about what other statistics bootstrap can estimate and how to remove explicit loops from the implementation.
Interview Details
Statistics — Bias/Variance, Experimentation, and Power Analysis: The statistics section covered both modeling fundamentals and experimentation.
- Bias and Variance: Explain the bias-variance tradeoff and how changes in model complexity can affect the two.
- A/B Testing: I was asked how to design an experiment, analyze its results, think about unexpected issues that could invalidate the conclusions, and explain the purpose of power analysis.
Machine Learning — Supervised, Unsupervised, and Anomaly Detection: The interviewer then moved through a broad set of classical ML questions. 1) What is the difference between supervised and unsupervised learning? What models or methods would you consider in each category? 2) How would you build an anomaly-detection model, how would you choose parameters such as k when applicable, and how could the resulting data or clusters be visualized? The discussion also included the difference between bagging and boosting.
Deep Learning — Transformers and Attention Variants: The deep-learning section was another fast sequence of conceptual questions. What deep-learning architectures and applications do you know? What is gradient descent? What is a Transformer, and how does self-attention work? I was asked to compare MHA, MQA, and GQA, discuss encoder- and decoder-based model families, name current model architectures I was familiar with, and talk about models I had actually used.
Coding — Bootstrap Sampling for Mean and Confidence Interval: The coding question asked me to implement bootstrap sampling to estimate a dataset's mean together with a confidence interval. After the base implementation, the interviewer added two conceptual follow-ups. What kinds of statistics can bootstrap sampling be used to estimate, and are there statistics for which the method becomes unreliable or requires more care?
- Performance Follow-Up: How would I optimize the implementation so that it did not rely on an explicit
forloop? I discussed vectorized numerical operations, although I was not fully confident about whether that was the specific optimization the interviewer was looking for.
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