DA0-002 Practice Exam 63 — 20 Questions

Question 1

A data analyst sees this error in the ETL logs. What is the most likely cause?

Accepted Answer

The underlying data source was modified after the last refresh. The error indicates that the materialized view's underlying data has changed since its last refresh. Materialized views rely on change tracking (e.g., logs or timestamps) to perform incremental refreshes. If the source data was modified after the last refresh, the view cannot be incrementally refreshed—a full refresh is required instead. This mismatch between the view's snapshot and the source data is a common cause of refresh failures in ETL processes.

Answer

The source table was dropped

Answer

The analyst does not have permission to refresh the view

Answer

There is a network connection timeout

Question 2

A company needs to store raw data from IoT sensors for future machine learning projects. The data is expected to be massive and in various formats. Which storage solution is most appropriate?

Accepted Answer

Data lake. A data lake stores raw data in its native format without predefined schema, ideal for large volumes of varied data for future use.

Answer

Data mart

Answer

Data warehouse

Answer

Relational database

Question 3

Which THREE of the following are best practices when performing data extraction for a data pipeline?

Accepted Answer

Implementing error handling and logging. Implementing error handling and logging is a critical best practice in data pipeline extraction. It ensures that failures (e.g., network timeouts, authentication errors, or schema mismatches) are captured and can be diagnosed without data loss or silent corruption, which is essential for maintaining pipeline reliability and auditability.

Answer

Performing a full refresh every time

Answer

Ignoring data quality issues during extraction

Question 4

An analyst creates a scatter plot with three variables: X, Y, and a third variable represented by the size of the markers. This chart is called a:

Accepted Answer

Bubble chart. A bubble chart is a variation of a scatter plot where a third numeric variable is encoded by the size (area) of the markers. This allows the visualization of three dimensions of data simultaneously on a two-dimensional plane, making it the correct choice for the described chart.

Answer

Heat map

Answer

Treemap

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Waterfall chart

Question 5

Drag and drop the steps to resolve data integration conflicts in the correct order.

Accepted Answer

Step 1: Identify conflicts, Step 2: Analyze conflicts, Step 3: Standardize data, Step 4: Transform data, Step 5: Merge data. Conflict resolution starts with identification, analysis, standardization, transformation, and merging.

Answer

Step 1: Identify conflicts, Step 2: Standardize data, Step 3: Analyze conflicts, Step 4: Transform data, Step 5: Merge data

Answer

Step 1: Analyze conflicts, Step 2: Identify conflicts, Step 3: Standardize data, Step 4: Transform data, Step 5: Merge data

Answer

Step 1: Identify conflicts, Step 2: Analyze conflicts, Step 3: Transform data, Step 4: Standardize data, Step 5: Merge data

Question 6

An analyst needs to communicate a data insight about a sudden drop in website traffic. Which communication method should be used first?

Accepted Answer

Schedule a live meeting to walk through the findings.. A sudden drop in website traffic is a critical, time-sensitive insight that requires immediate discussion and validation. A live meeting allows the analyst to present the data, answer questions, and collaboratively determine the root cause (e.g., a server outage, SEO penalty, or broken tracking code) before taking action. This aligns with the DA0-001 domain of Communicating Data Insights, where urgency and context demand interactive, real-time communication.

Answer

Update the dashboard without notification.

Answer

Post on the company wiki.

Answer

Send an email with a data dump.

Question 7

A data analyst needs to display the distribution of customer ages in a dataset. The ages range from 18 to 85, and the analyst wants to see the shape of the distribution and identify any outliers. Which chart type should be used?

Accepted Answer

Histogram. A histogram shows the distribution of a continuous variable, while a box plot shows quartiles and outliers. The question asks for distribution shape, so histogram is more appropriate.

Answer

Scatter plot

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Bar chart

Answer

Box plot

Question 8

A table Orders has OrderID (primary key), CustomerID, and CustomerEmail. During analysis, it is found that CustomerID uniquely identifies CustomerEmail. Which normal form is violated if both CustomerID and CustomerEmail are stored in this table?

Accepted Answer

Third normal form (3NF). The table violates Third Normal Form (3NF) because CustomerEmail is transitively dependent on CustomerID, which is not a candidate key. In 3NF, every non-key attribute must depend only on the primary key (OrderID), not on another non-key attribute. Since CustomerID uniquely identifies CustomerEmail, CustomerEmail depends on CustomerID, not directly on OrderID, creating a transitive dependency.

Answer

Second normal form (2NF)

Answer

No violation

Answer

First normal form (1NF)

Question 9

Which data sampling method involves selecting every k-th element from a list after a random start?

Accepted Answer

Systematic sampling. Systematic sampling selects every k-th item after a random start.

Answer

Cluster sampling

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Stratified sampling

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Simple random sampling

Question 10

A data analyst runs the following query: SELECT DISTINCT city FROM customers. What is the primary purpose of using the DISTINCT keyword in this query?

Accepted Answer

To remove duplicate city names. DISTINCT removes duplicate rows from the result set. In this query, it returns each unique city name only once.

Answer

To sort the cities alphabetically

Answer

To count the number of cities

Answer

To filter cities that start with a specific letter

Question 11

After merging two datasets, an analyst finds that the resulting dataset has many null values in some columns. Which TWO steps should the analyst take to address this? (Select two.)

Accepted Answer

Impute nulls with the median.. Imputing nulls with the median is a standard technique for handling missing numerical data, especially when the distribution is skewed or contains outliers. The median is robust to extreme values and preserves the central tendency of the column, making it a safe choice for many analytical models. This approach avoids data loss while maintaining statistical integrity.

Answer

Ignore nulls and proceed.

Answer

Remove all rows with nulls.

Answer

Replace nulls with a placeholder value like 'Unknown'.

Question 12

A company is implementing a data lifecycle management policy. Which stage occurs immediately after data is created?

Accepted Answer

Storage. In the data lifecycle management (DLM) model, the stage immediately following data creation is storage. Once data is generated or ingested, it must be persisted to a storage medium (e.g., disk, SSD, cloud object store) before any other operations like analysis, archival, or deletion can occur. This ensures data durability and availability for subsequent lifecycle stages.

Answer

Deletion

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Archival

Answer

Analysis

Question 13

Which TWO of the following are examples of unstructured data? (Select 2)

Accepted Answer

MP4 video. A is correct because MP4 video files contain binary data that lacks a predefined schema or tabular structure, making them a classic example of unstructured data. Unlike structured data, MP4 files store audiovisual content in a container format that cannot be easily queried or analyzed without specialized processing.

Answer

CSV file

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XML file

Answer

JSON document

Question 14

A data engineer is designing a data pipeline where raw data is loaded into a cloud data warehouse (Snowflake) and then transformed using SQL. This approach is called:

Accepted Answer

ELT. ELT (Extract, Load, Transform) loads raw data first, then transforms it within the warehouse, which is suitable for modern cloud warehouses.

Answer

ETL

Answer

Data migration

Answer

Data wrangling

Question 15

Drag and drop the steps to implement a data classification policy in the correct order.

Accepted Answer

Define classification levels, assign ownership, label data, enforce access control, train employees. Classification involves defining levels, assigning ownership, labeling, access control, and training.

Answer

Train employees, define classification levels, assign ownership, label data, enforce access control

Answer

Label data, define classification levels, assign ownership, enforce access control, train employees

Answer

Define classification levels, label data, assign ownership, enforce access control, train employees

Question 16

Which THREE are considered best practices in dashboard design? (Select three.)

Accepted Answer

Using heat maps to visualize correlation. Heat maps effectively visualize correlation by using color intensity to represent the strength of relationships between two variables, making patterns and outliers immediately apparent. This aligns with best practices for dashboard design, which prioritize clarity and rapid insight over decorative elements.

Answer

Using 3D charts to add depth

Answer

Including every data point in the dashboard

Question 17

A data analyst is preparing a presentation on customer churn. The audience consists of both technical and non-technical stakeholders. Which visualization approach is most effective?

Accepted Answer

A simple bar chart showing churn rate by segment.. A simple bar chart showing churn rate by segment is most effective because it directly communicates the key metric (churn rate) across categorical segments (e.g., customer demographics or plan types) in a format that is immediately understandable to both technical and non-technical stakeholders. Bar charts excel at comparing discrete categories without requiring statistical literacy, making them ideal for mixed audiences in a presentation context.

Answer

A box plot showing distribution of churn.

Answer

A heatmap showing correlation of churn factors.

Answer

A scatter plot with multiple variables.

Question 18

A data analyst is using Power BI to create a report that shows sales by region. The data includes duplicate rows for some transactions due to a data entry error. The analyst needs to count only unique transactions. Which DAX function should be used to create a measure for unique count?

Accepted Answer

DISTINCTCOUNT. DISTINCTCOUNT is the DAX function specifically for counting unique values in a column.

Answer

COUNT

Answer

COUNTROWS

Answer

SUMX

Question 19

A data analyst is building a linear regression model to predict sales based on advertising spend. The analyst notices that the residuals are not normally distributed and have a non‑constant variance. Which of the following transformations is most appropriate to apply to the dependent variable?

Accepted Answer

Logarithmic transformation. The logarithmic transformation is the most appropriate choice because it stabilizes non‑constant variance (heteroscedasticity) and helps make the residuals more normally distributed, which are key assumptions for linear regression. By compressing the scale of the dependent variable (sales), it reduces the impact of large values and often linearizes multiplicative relationships, such as diminishing returns from advertising spend.

Answer

Standardization (z-score)

Answer

Normalization (min-max scaling)

Answer

Square root transformation

Question 20

A data analyst is preparing to build a predictive model. Which TWO steps are essential to ensure model validity? (Choose two.)

Accepted Answer

Perform cross-validation. Cross-validation is essential for model validity because it partitions the data into multiple folds, training on k-1 folds and validating on the remaining fold, which provides a robust estimate of model performance and reduces overfitting. This technique ensures that the model generalizes well to unseen data by repeatedly testing different subsets, making it a standard practice in predictive modeling.

Answer

Increase model complexity

Answer

Avoid feature selection

Answer

Use the entire dataset for training