Ace Your Machine Learning Engineer Interview
Master the questions, showcase your expertise, and land your dream job.
- Curated list of high-impact interview questions
- Detailed STAR model answers for each question
- Practical tips and red‑flag warnings
- Competency‑based weighting to focus study effort
- Ready‑to‑use practice pack with timed rounds
Fundamentals
In a recent regression project, our model was either under‑fitting or over‑fitting depending on the complexity of the features.
I needed to explain to stakeholders why adjusting model complexity impacted performance.
I described bias as error from erroneous assumptions (under‑fitting) and variance as error from sensitivity to small fluctuations in the training data (over‑fitting). I illustrated with a simple polynomial fit graph showing low‑bias/high‑variance vs high‑bias/low‑variance curves.
The team understood the need to balance model complexity, leading us to adopt cross‑validation to select the optimal degree, which improved validation RMSE by 12%.
- How can you detect high bias in a model?
- What techniques reduce variance without increasing bias?
- Can you give an example where you deliberately increased bias?
- Clarity of definitions
- Use of concrete example
- Understanding of mitigation strategies
- Relevance to real‑world projects
- Vague description without distinction
- No example or mitigation technique
- Define bias and variance separately
- Explain how model complexity influences each
- Show visual or intuitive example
- Discuss methods to manage tradeoff (e.g., regularization, cross‑validation)
While building a fraud detection model, the positive class represented only 1% of transactions.
Improve detection performance without inflating false positives.
I applied resampling techniques: undersampled the majority class and oversampled the minority using SMOTE. I also experimented with class‑weight adjustments in the loss function and evaluated using precision‑recall curves rather than accuracy.
The final model achieved a recall of 85% at a precision of 70%, a significant improvement over the baseline 30% recall.
- When might undersampling be risky?
- Explain how SMOTE works.
- How do you choose the decision threshold?
- Recognition of imbalance impact
- Appropriate technique selection
- Metric justification
- Result quantification
- Only mentions accuracy as metric
- No discussion of trade‑offs
- Identify the imbalance ratio
- Choose appropriate resampling or weighting methods
- Select suitable evaluation metrics (PR‑AUC, F1)
- Iterate and validate
