DA0-002 Practice Test 19 — 15 Questions

Question 1

An analyst runs a simple linear regression with an R² value of 0.85. Which interpretation is correct?

Accepted Answer

85% of the variance in the dependent variable is explained by the independent variable.. R² represents the proportion of variance in the dependent variable explained by the independent variable. 0.85 means 85% is explained.

Answer

The slope of the regression line is 0.85.

Answer

The independent variable is 85% correlated with the dependent variable.

Answer

85% of the data points lie on the regression line.

Question 2

A data analyst is cleaning a dataset and identifies several outliers. Which TWO methods are appropriate for handling outliers?

Accepted Answer

Capping. Capping (winsorizing) and removal are common outlier treatments. Mean imputation is for missing values, and min-max normalization is scaling.

Answer

Mean imputation

Answer

Min-max normalization

Answer

Forward-fill

Question 3

Which data quality dimension ensures that data represents the real-world scenario correctly and without errors?

Accepted Answer

Accuracy. Accuracy means the data correctly reflects reality.

Answer

Completeness

Answer

Consistency

Answer

Timeliness

Question 4

You have a hierarchical table 'Employees' with columns emp_id, emp_name, manager_id (referencing emp_id). You need to generate a full reporting chain from a given employee up to the CEO. Which SQL construct is most appropriate?

Accepted Answer

Recursive CTE with UNION ALL. Recursive CTEs are designed for hierarchical data, allowing iteration through parent-child relationships. Non-recursive CTEs cannot loop. Self-join with multiple levels is possible but requires knowing the depth. Window functions are not suitable for tree traversal.

Answer

Non-recursive CTE

Answer

Window function with PARTITION BY

Answer

Self-join with multiple JOINs

Question 5

Which of the following data types is characterized by a flexible schema and is commonly represented using JSON or XML?

Accepted Answer

Semi-structured data. JSON and XML are examples of semi-structured data, which has a flexible schema unlike structured data (fixed schema) or unstructured data (no schema).

Answer

Unstructured data

Answer

Structured data

Answer

Relational data

Question 6

A financial analyst wants to compare the mean annual returns of three different investment strategies. Which statistical test is most appropriate?

Accepted Answer

One-way ANOVA. ANOVA is used to compare means of three or more groups.

Answer

Chi-square test

Answer

Paired t-test

Answer

Two-sample t-test

Question 7

Which of the following data sources is most likely to generate streaming data?

Accepted Answer

IoT sensors. Streaming data is continuously generated from sources like IoT sensors, clickstreams, and social media feeds.

Answer

Transactional database

Answer

Flat file

Answer

API

Question 8

A database designer wants to improve query performance on a large table that is frequently filtered by multiple columns. Which TWO types of indexes could be beneficial? (Select TWO).

Accepted Answer

Composite index. Composite indexes cover multiple columns, and B-tree indexes are general-purpose and support range queries, both useful for filtering on multiple columns.

Answer

Bitmap index

Answer

Hash index

Answer

Full-text index

Question 9

A company is ingesting data from multiple sources into a cloud data warehouse. They decide to load the data raw and then perform transformations within the warehouse. Which approach does this describe?

Accepted Answer

ELT. ELT (Extract, Load, Transform) loads raw data first, then transforms it inside the data warehouse, as opposed to ETL which transforms before loading.

Answer

Data lake ingestion

Answer

ETL

Answer

Stream processing

Question 10

A data analyst needs to combine data from two tables: one containing customer information and another containing order details. The analyst wants to include all customers, even those who have not placed any orders. Which type of join should be used?

Accepted Answer

LEFT JOIN. A LEFT JOIN returns all rows from the left table (customers) and matching rows from the right table (orders). If a customer has no orders, the order columns will contain NULLs. This satisfies the requirement to include all customers, even those without orders.

Answer

FULL OUTER JOIN

Answer

INNER JOIN

Answer

RIGHT JOIN

Question 11

A market researcher conducts a survey with questions like "What is your favorite brand?" and "How many units do you purchase per year?" Which data types correspond?

Accepted Answer

Qualitative & Quantitative. 'favorite brand' is a categorical label (qualitative data), while 'units purchased per year' is a numerical count (quantitative data). The question explicitly pairs these two distinct data types, matching the definition of qualitative (non-numeric categories) and quantitative (numeric measurements).

Answer

Quantitative & Qualitative

Answer

Both quantitative

Answer

Both qualitative

Question 12

An OLTP system processes thousands of transactions per second. Which property ensures that a transaction is fully completed or fully rolled back, preventing partial updates?

Accepted Answer

Atomicity. Atomicity guarantees that a transaction is treated as a single unit, completed entirely or not at all.

Answer

Isolation

Answer

Durability

Answer

Consistency

Question 13

A data engineer is comparing data warehouses and data lakes. Which statement accurately describes a data warehouse?

Accepted Answer

Optimized for complex queries on structured data. A data warehouse is optimized for complex queries on structured data because it uses a schema-on-write approach, where data is cleaned, transformed, and organized into relational tables (e.g., star or snowflake schemas) before loading. This pre-processing enables efficient execution of aggregations, joins, and reporting queries using SQL, making it ideal for business intelligence and analytics. In contrast, data lakes store raw data in native formats and rely on schema-on-read, which is less performant for structured query patterns.

Answer

Typically stores data in object storage

Answer

Stores raw, unprocessed data

Answer

Uses schema-on-read

Question 14

Which of the following is an example of semi-structured data?

Accepted Answer

A JSON file. Semi-structured data has tags or markers to separate data elements, like JSON or XML.

Answer

A CSV file without header

Answer

An image file

Answer

A table in a relational database

Question 15

In a Power BI report, a user wants to create a measure that calculates total sales for the current year up to today. Which DAX function should they use?

Accepted Answer

TOTALYTD. TOTALYTD is a time intelligence function that calculates year-to-date values.

Answer

CALCULATE

Answer

SUMX

Answer

SAMEPERIODLASTYEAR