CompTIA DY0-001 - CompTIA DataX Exam

→ Embeddings (e.g., word2vec, sentence transformers) are vector representations of text that capture semantic similarity. They allow comparison of conceptual meaning between sentences in a high-dimensional space, which is essential for tasks like semantic similarity or clustering.

Why the other options are incorrect:

B: Extrapolation predicts values beyond a dataset’s range — not relevant here.

C: Sampling reduces data volume but doesn’t aid in similarity analysis.

D: One-hot encoding captures presence of words but lacks semantic understanding.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 6.3:“Embeddings transform text into numeric vectors, enabling similarity computation and semantic analysis.”

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→ R² (coefficient of determination) quantifies how much of the variance in the dependent variable is explained by the model. A higher R² means a better fit to the data, making it the metric to maximize for explanatory power in regression analysis.

Why the other options are incorrect:

A: Accuracy is used in classification, not regression.

C: p-values test statistical significance of coefficients, not overall model fit.

D: AUC (Area Under the Curve) applies to classification models, not regression.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 3.2:“R² is a regression performance metric indicating the proportion of variance explained by the independent variables.”

→ The difference between the benchmark RMSE (1,000) and the new model RMSE (995) is minimal and may not justify replacing the existing model. Though the adjusted R² is decent, business decisions should be based on whether the improvement is statistically and practically significant.

Why the other options are incorrect:

A: The RMSE improvement is marginal and may not be worth deployment effort.

B: The adjusted R² of 0.75 is moderate, not necessarily “exceptionally strong.”

D: The claim about industry standards is unsupported and not universally true.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 3.2:“Model selection must consider both statistical improvement and practical significance.”

Data Science Best Practices, Chapter 8:“Small improvements in performance metrics must be evaluated in the context of deployment cost and business impact.”

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Given the requirements:

Minimized file size

Fast ingestion

Schema preservation (including data types)

The most appropriate format is:

→ Parquet – It is a columnar storage file format developed for efficient data processing. Parquet files are compressed, support schema embedding, and enable fast columnar reads, making them ideal for analytical workloads and big data environments.

Why the other options are incorrect:

A. JSON: Text-heavy and lacks native support for data types/schema.

C. XML: Verbose and has poor performance in storage and ingestion speed.

D. CSV: Flat structure, doesn’t store data types or schema, and can be large in size.

Official References:

CompTIA DataX (DY0-001) Official Study Guide – Section 6.2 (Data Storage Formats):“Parquet is a preferred format for data analysis as it provides efficient compression and encoding with embedded schema information, making it ideal for minimal storage and fast ingestion.”

Apache Parquet Documentation:“Parquet is designed for efficient data storage and retrieval. It includes schema support and works best for analytics use cases.”

Parquet is a columnar storage format that automatically includes schema (data types), uses efficient compression to minimize file size, and enables very fast reads for analytic workloads.

→ FULL OUTER JOIN returns all rows from both tables, inserting NULLs where no match exists. This join includes the maximum possible number of records — all matches, plus all unmatched records from both sides.

Why the other options are incorrect:

A: INNER JOIN returns only matching rows — less total data.

B & C: LEFT/RIGHT JOIN include all rows from one table only.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 5.2:“A FULL OUTER JOIN maximizes data volume by including all matched and unmatched records from both tables.”

SQL for Data Science, Chapter 4:“Use FULL OUTER JOIN when the goal is to preserve every record from both datasets regardless of match.”

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→ LASSO (Least Absolute Shrinkage and Selection Operator) regression minimizes the squared residuals (e²), just like OLS, but adds an L1 penalty to encourage sparsity in the coefficients. Thus, the residual component minimized is still the sum of squared errors.

Why the other options are incorrect:

A: |e| is absolute error, not used in standard LASSO objective.

B: e is the error term, but minimization applies to its squared version.

C: Minimizing to exactly 0 is idealistic but not realistic.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 3.3:“LASSO minimizes squared errors with an additional L1 regularization term.”

Elements of Statistical Learning, Chapter 6:“LASSO regression uses the same residual sum of squares (e²) as OLS for error measurement, with an added constraint.”

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→ An Autoregressive (AR) model is ideal when past values of a time series are used to predict future values. Since the only input is historical price data of copper, AR is the most appropriate technique.

Why the other options are incorrect:

B: Moving average smooths noise but doesn’t model the dependencies for prediction.

C: Dynamic time warping is used for measuring similarity between time series, not forecasting.

D: Relative strength is a financial metric used for comparing asset performance — not a forecasting technique.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 3.5:“Autoregressive models are used when the goal is to predict future values based solely on past values in a univariate time series.”

Time Series Analysis and Forecasting, Chapter 5:“AR models capture the temporal dependencies in time series data and are foundational in time-based prediction.”

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→ A basic artificial neural network (ANN) consists of:

An input layer to receive data

At least one hidden layer to process the data

An output layer to produce predictions

These three layers form the minimal architecture required for learning and transformation.

Why the other options are incorrect:

A: Pooling layers are used in CNNs, not core ANN structure.

B: Convolutional layers are specific to CNNs.

D: Dropout is a regularization technique, not a required component.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 4.3:“ANNs must include an input layer, hidden layer(s), and an output layer to form a complete learning structure.”

Deep Learning Fundamentals, Chapter 3:“At a minimum, a neural network includes input, hidden, and output layers to process and propagate data.”

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→ Extrapolated data refers to making predictions about data points that fall outside the observed range or distribution. Since the sample data (80%) is heavily skewed toward a small subset of professions and locations, predicting results for the remaining, unrepresented professions and regions involves extrapolation.

Why the other options are incorrect:

A: Interpolation occurs within the bounds of observed data — not the issue here.

C: In-sample data refers to training data, which is overrepresented in this case.

D: Out-of-sample data is a concern in generalization but extrapolation is more specific here.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 3.2:“Extrapolation introduces risk when models are used outside the range of data they were trained on, especially if certain subgroups are underrepresented.”

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→ A Normal distribution is appropriate for modeling variables that cluster around a central mean and have natural variability — such as bus arrival times around a scheduled time. Even though the bus is scheduled hourly, real-world factors (traffic, weather, etc.) will cause actual arrival times to vary normally around the scheduled mean.

Why the other options are incorrect:

A: Binomial is for discrete yes/no trials, not continuous time modeling.

B: Exponential models time between events, typically memoryless — not suitable for arrival distributions with a known mean and variance.

D: Poisson models event counts per time interval, not the timing of continuous events like arrival times.

Official References:

CompTIA DataX (DY0-001) Study Guide – Section 1.3:“Normal distributions are appropriate for modeling real-world continuous variables that fluctuate around a central tendency, such as scheduled processes.”

Statistics for Data Science, Chapter 4 – Distributions:“Arrival times of periodic services often approximate a normal distribution when influenced by continuous variation.”

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