Free Amazon Web Services MLA-C01 Practice Exam with Questions & Answers | Set: 6

Logistic regression is a suitable modeling approach for this requirement because it is designed for binary classification problems, such as predicting whether a customer will require long-term support ( " yes " or " no " ). It calculates the probability of a particular class and is widely used for tasks like this where the outcome is categorical.

Option B is correct because AWS Glue provides a built-in Detect PII transform that can detect, mask, or remove personally identifiable information with minimal custom development. AWS documentation says the Detect PII transform can process predefined AWS-managed PII entity types and supports actions such as removing or masking values. The examples in AWS docs explicitly mention sensitive entities such as phone numbers and addresses, which directly match the problem statement.

The question specifically asks for the least development effort. That wording makes AWS Glue Detect PII the strongest answer because it is a native transformation capability rather than a custom code-heavy workflow. AWS also documents fine-grained sensitive data detection features that let you apply actions per entity type, improving usability and reducing the need to build custom parsing and redaction logic yourself. This is much easier than creating Lambda-based transformation code or custom text-cleaning logic inside another ML preprocessing tool.

The other options are less suitable. Amazon Bedrock Guardrails is not the standard AWS service documented for bulk ETL-style redaction of training text files in this context. S3 Object Lambda would require more custom engineering to inspect and redact each object. SageMaker Data Wrangler custom transformation would also involve extra implementation work compared with using a purpose-built Glue transform. Because the call center already has text output and simply needs regulated fields like names, addresses, and phone numbers removed before training, the AWS-native low-effort solution is AWS Glue Detect PII. Therefore, the best verified answer is B.

The requirement is event-driven automation when new data arrives in Amazon S3, followed by training and model registration. Amazon EventBridge natively supports S3 object creation events and can trigger downstream workflows immediately.

By using EventBridge to start an AWS Step Functions workflow that includes a training step and a SageMaker Model Registry registration step, the pipeline runs automatically as soon as new data is uploaded—well within the 24-hour requirement.

Option A introduces unnecessary polling and delay. Option B is time-based and does not ensure alignment with data readiness. Option C is invalid because S3 Lifecycle rules manage object transitions, not workflow execution.

Therefore, EventBridge-triggered Step Functions is the correct solution.

In regression problems such as house price prediction, extreme values can significantly distort model learning. In this dataset, the presence of a large mansion and an extremely small apartment represents clear outliers in the Square Meters feature. According to AWS Machine Learning best practices, outliers can disproportionately influence loss functions (such as mean squared error), leading to poor predictions for the majority of typical data points.

Removing these outliers helps the model focus on learning patterns that apply to the majority of houses and apartments, which aligns with the requirement to produce accurate predictions for typical properties. After removing outliers, applying a log transformation to the Square Meters feature further improves model performance by reducing skewness and stabilizing variance. Log transformations are commonly recommended in AWS and general ML documentation when numerical features span multiple orders of magnitude.

Option B is incorrect because normalization alone does not address the undue influence of extreme outliers. Option C and D are incorrect because one-hot encoding is intended for categorical variables, not continuous numerical features such as square meters.

Therefore, removing outliers and applying a log transformation is the most statistically sound preprocessing approach.

An oscillating loss pattern during training with stochastic gradient descent (SGD) is a strong indicator that the learning rate is too high. When the learning rate is excessive, the optimizer takes overly large steps during gradient updates, causing the model to repeatedly overshoot the optimal minimum of the loss function. This results in unstable convergence behavior, where training and validation loss decrease briefly and then increase again in a repeating cycle.

AWS Machine Learning documentation and general deep learning best practices recommend reducing the learning rate when training loss and validation loss both remain high and fluctuate rather than steadily decreasing. Lowering the learning rate allows the optimizer to take smaller, more precise steps toward the minimum, leading to smoother convergence and improved generalization on the test dataset.

Option A, early stopping, is used primarily to prevent overfitting when validation loss increases while training loss continues to decrease. In this scenario, both losses remain high and unstable, indicating an optimization issue rather than overfitting.

Option B is incorrect because increasing the test set size does not affect the training dynamics or convergence behavior of the model.

Option C would worsen the problem, as increasing the learning rate would further amplify oscillations and instability.

Therefore, decreasing the learning rate is the correct corrective action to stabilize SGD training and improve model performance.

Change the number of samples used in each iteration of training

Correct selection:

Change the batch size

Why:

Increasing the batch size reduces the number of iterations per epoch, which can significantly shorten training time while maintaining model quality when tuned appropriately. AWS explicitly recommends batch size tuning as a primary performance optimization.

Increase the number of instances used during training

Correct selection:

Use the SageMaker AI distributed data parallelism (SMDDP) library

Why:

SMDDP is designed to efficiently distribute training data across multiple GPU instances with optimized gradient synchronization. This accelerates training without affecting model convergence or accuracy, unlike naive scaling approaches.

Stop training before the maximum number of epochs are reached if performance is sufficient and not improving

Correct selection:

Use early stopping on the training job

Why:

Early stopping automatically terminates training when validation metrics stop improving. AWS recommends this to reduce wasted compute time while preserving optimal model performance.

Option D is correct because the company’s primary goal is to identify as many fraudulent transactions as possible. In AWS documentation, recall is defined as TP / (TP + FN), where TP is true positives and FN is false negatives. Recall measures how well a model finds all actual positive cases. In a fraud-detection setting, the “positive” class is the fraudulent transaction, so maximizing recall means minimizing missed fraud cases.

AWS documentation also explains the business tradeoff clearly: a use case that needs to correctly predict as many positive examples as possible should prioritize high recall, even if that means accepting some additional false positives and therefore only moderate precision. That matches this question exactly, because the requirement is not to be most selective or most balanced overall; it is specifically to catch the largest possible number of fraudulent transactions.

The other metrics are less aligned to the stated goal. Precision focuses on how many predicted fraud cases are actually fraud, which is most important when false positives are very costly. F1 score balances precision and recall, but the question does not ask for balance; it asks for finding as many fraudulent transactions as possible. AUC is useful for overall ranking and threshold-independent model discrimination, but it is not the most direct metric for optimizing missed-fraud detection in this scenario. Based on AWS metric definitions, when the cost of missing true positives is the main concern, recall is the best evaluation metric. Therefore, the best verified answer is D.

Class imbalance occurs when one class significantly outnumbers another, causing models to bias predictions toward the majority class. In this case, images without defects (1,800) vastly outnumber images with defects (200). AWS ML best practices recommend oversampling the minority class to improve class representation without discarding valuable data.

Oversampling techniques—such as duplicating minority samples or applying data augmentation—help the model better learn defect-related features. This approach preserves all available data and improves recall and precision for underrepresented defect classes.

Option B is incorrect because undersampling the minority class would further worsen imbalance. Option A unnecessarily reduces dataset size. Option D does not address the imbalance problem.

Thus, oversampling defect images is the correct solution.

The correct answer is A. Enable CloudTrail log file integrity validation.

AWS CloudTrail provides the ability to record API calls made to AWS services and delivers log files to an Amazon S3 bucket. For organizations that need to ensure the authenticity and integrity of these log files, AWS recommends enabling log file integrity validation. This feature applies a hash function to each log file and stores the hash separately, allowing you to verify that the logs have not been altered, deleted, or tampered with after delivery.

Enabling log file integrity validation is critical in ML operations when auditing model training pipelines, production inference calls, or system access patterns across accounts. It ensures that security-sensitive API activity is accurately recorded and verifiable. In multi-account environments managed by AWS Organizations, this validation provides an extra layer of trust when logs are consolidated from multiple accounts.

Option B, creating a multi-Region trail, ensures that API activity across regions is logged but does not inherently guarantee the integrity of logs. Option C, creating an organization trail, centralizes logging for all accounts, which is valuable for governance, but again does not automatically provide verification of log integrity. Option D, enabling CloudWatch Logs delivery, allows real-time monitoring and alerting but does not address the verification of historical log files.

By enabling log file integrity validation, organizations can cryptographically verify each log file, detect unauthorized changes, and meet compliance requirements for secure ML monitoring and auditing. This aligns with AWS best practices for ML solution monitoring, maintenance, and security, ensuring reliable tracking of model operations and API usage across distributed ML systems.

City (name): One-hot encoding

Type_year (type of home and year the home was built): Feature splitting

Size of the building (square feet or square meters): Standardized distribution

City (name): One-hot encoding

Why? The " City " is a categorical feature (non-numeric), so one-hot encoding is used to transform it into a numeric format. This encoding creates binary columns for each unique category (e.g., cities like " New York " or " Los Angeles " ), which the model can interpret.

Type_year (type of home and year the home was built): Feature splitting

Why? " Type_year " combines two pieces of information into one column, which could confuse the model. Feature splitting separates this column into two distinct features: " Type of home " and " Year built, " enabling the model to process each feature independently.

Size of the building (square feet or square meters): Standardized distribution

Why? Size is a continuous numerical variable, and standardization (scaling the feature to have a mean of 0 and a standard deviation of 1) ensures that the model treats it fairly compared to other features, avoiding bias from differences in feature scale.

By applying these feature engineering techniques, the ML engineer can ensure that the input data is correctly formatted and optimized for the model to make accurate predictions.