DA0-002 Practice Test 8 — 10 Questions

Question 1

A data analyst creates a dashboard for executives to monitor quarterly sales. Which best practice ensures the dashboard is effective?

Accepted Answer

Place the most important metric in the top-left corner with simple charts.. Placing the most important metric in the top-left corner leverages the natural reading pattern (left-to-right, top-to-bottom) to immediately draw the executive's attention to the key insight. Using simple charts (e.g., bar or line charts) reduces cognitive load, enabling rapid comprehension of quarterly sales trends without distracting details. This aligns with dashboard design principles that prioritize clarity and actionability over data density.

Answer

Use a dark background with bright colors for contrast.

Answer

Include raw data tables for detailed analysis.

Answer

Use as many charts as possible to show all data.

Question 2

A retail company has a data warehouse that integrates sales data from multiple sources including online transactions, in-store POS, and third-party marketplaces. The data team recently updated the ETL pipeline to add a new data source: mobile app purchases. After the update, the daily sales report shows a 15% increase in total sales compared to the previous day, which is unexpected because the mobile app is new and only contributed 2% of sales in tests. The report is created by a SQL script that aggregates sales by date and runs every morning. The data team needs to identify the cause of the discrepancy. Which of the following should the team do first?

Accepted Answer

Verify that the date filter in the SQL script is correct and not including future dates.. The correct first step because an unexpected 15% increase in total sales, especially when the new mobile app source accounts for only 2% in tests, suggests a data integrity issue rather than a real sales surge. The most common cause is a date filter error in the SQL script, such as including future dates or applying an incorrect date range, which would inflate the daily total. Verifying the date filter is a quick, low-effort check that can confirm the data source before investigating more complex issues like double-counting (Option D). Options B and C are premature: comparing raw transaction counts is a secondary step after confirming the date filter, and assuming the increase is real (C) ignores the most likely data problem.

Answer

Compare the raw transaction counts from each source for that day.

Answer

Assume the increase is due to the mobile app and update the forecast.

Answer

Check if the ETL pipeline is double-counting transactions from the mobile app source.

Question 3

A data analyst is cleaning text data in a SQL database. Which THREE string functions are commonly used to standardize and clean text? (Choose three.)

Accepted Answer

REPLACE. TRIM removes leading/trailing spaces, UPPER/LOWER standardize case, REPLACE substitutes substrings. CONCAT concatenates strings, LENGTH returns length, SUBSTRING extracts part of string.

Answer

LENGTH

Answer

CONCAT

Question 4

A data analyst is using pandas to clean a DataFrame that contains missing values in the 'age' and 'income' columns. Which THREE pandas methods are appropriate for handling missing data? (Select THREE).

Accepted Answer

dropna(). Common pandas methods for missing data include dropna (remove rows with NaN), fillna (replace NaN with a value), and apply with a custom function. Merge is for combining DataFrames; pivot_table is for reshaping.

Answer

pivot_table()

Answer

merge()

Question 5

A healthcare organization is building a data warehouse to support population health analytics. The data sources include: (1) an electronic health record (EHR) system with a relational database containing patient demographics, diagnoses, and medications; (2) a claims system that generates CSV files daily; (3) patient-generated health data from mobile apps via a REST API returning JSON. The data engineer needs to design a data acquisition process that runs nightly. The EHR system has a change tracking mechanism that logs changes with timestamps. The claims CSV files are appended daily. The API supports filtering by date. The data warehouse uses a star schema with fact and dimension tables. The engineer must ensure data consistency and minimize load times. Which approach should the engineer take?

Accepted Answer

Extract only new and changed EHR data using change tracking, extract the full claims CSV (since it's append-only), and extract API data filtered by the last extraction date. It uses incremental extraction for the EHR system (via change tracking) and the API (via date filtering), while performing a full extraction of the claims CSV since it is append-only and small enough to reload nightly. This minimizes load times by avoiding full re-extraction of large, slowly changing datasets, and ensures data consistency by capturing only new or modified records. The star schema in the data warehouse is then populated efficiently from these targeted extracts.

Answer

Perform a full extraction of all data from all sources every night and load directly into the data warehouse

Answer

Use a staging area to land all raw data first, then transform and load

Answer

Extract the EHR data using change tracking, extract the full claims CSV, and extract the API data using a full dump

Question 6

A data analyst creates a scatter plot showing the relationship between advertising spend and revenue. The plot shows a strong positive correlation. Which of the following should the analyst include in the report to ensure accurate communication?

Accepted Answer

Include a note that correlation does not imply causation.. Correlation does not imply causation. It is important for the analyst to include this caveat to prevent misinterpretation of the relationship. Option B is incorrect because a bar chart is not appropriate for showing the relationship between two continuous variables. Option C is incorrect because removing outliers without justification can distort the analysis; outliers should be handled transparently. Option D is incorrect because while a trend line could be added, it is not mandatory and the question specifically asks for ensuring accurate communication, which is primarily about the correlation-causation warning.

Answer

Replace the scatter plot with a bar chart.

Answer

Remove any outliers from the plot.

Answer

Add a trend line to the scatter plot.

Question 7

An analyst is presenting findings to stakeholders. Which TWO techniques effectively communicate uncertainty in data? (Choose TWO.)

Accepted Answer

Include confidence intervals.. Confidence intervals provide a range of values that likely contain the true population parameter, offering a clear measure of uncertainty around a point estimate. This technique is fundamental in inferential statistics and directly communicates the precision of the data, helping stakeholders understand the reliability of the findings.

Answer

Use only point estimates.

Answer

Remove all outliers from the data.

Answer

State exact numbers without ranges.

Question 8

A company uses a NoSQL document database to store product catalogs. Each product document includes fields like product_id, name, category, and price. The operations team frequently queries by product_id and by category. Which type of NoSQL database is being used, and what should be created to optimize queries by category?

Accepted Answer

Document database; create an index on category. The question explicitly states a document database is used, and the operations team frequently queries by category. In a document database like MongoDB, creating an index on the category field optimizes these queries by allowing the database to quickly locate documents without scanning every document in the collection. This is the standard approach for improving query performance on non-primary-key fields in document stores.

Answer

Key-value store; create a secondary index on category

Answer

Graph database; create a relationship between products

Answer

Wide-column store; create a column family for category

Question 9

A data analyst needs to present the correlation between advertising spend and website traffic. Which chart type is most appropriate?

Accepted Answer

Scatter plot. A scatter plot is the most appropriate chart type for visualizing the correlation between two continuous variables, such as advertising spend and website traffic. It displays individual data points on a Cartesian plane, allowing the analyst to assess the strength, direction, and form of the relationship (e.g., linear, non-linear, or no correlation). This aligns with the DA0-001 objective of selecting the correct visualization for bivariate analysis.

Answer

Bar chart

Answer

Line chart

Answer

Pie chart

Question 10

A data engineer is designing a data warehouse for a multinational corporation. The company has sales data from different regions with varying currencies and date formats. To ensure consistency, which data concept should be applied to standardize the data before loading into the warehouse?

Accepted Answer

Data transformation. Data transformation is the correct concept because it involves converting data from source formats (e.g., different currencies and date formats) into a consistent, standardized format before loading into the data warehouse. This process includes applying conversion rules, such as using ISO 8601 for dates and a single base currency (e.g., USD) with exchange rate tables, ensuring uniformity across all regional data. Without transformation, the warehouse would contain incompatible data types, breaking referential integrity and analytical queries.

Answer

Data cleansing

Answer

Data profiling

Answer

Data masking