DA0-002 Practice Test 40 — 15 Questions

Question 1

An analyst is using Python pandas and has a DataFrame 'sales' with columns 'date', 'product', 'revenue'. They need to create a pivot table showing total revenue per product per month. Which pandas function is most appropriate?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

sales.pivot_table(index='product', columns='month', values='revenue', aggfunc='sum'). pivot_table is specifically designed to reshape data and aggregate values based on index and columns.

Answer

sales.groupby(['product', 'month']).sum()

Answer

sales.pivot(index='product', columns='month', values='revenue')

Answer

sales.melt(id_vars=['product'], value_vars=['month', 'revenue'])

Question 2

A dashboard automatically refreshes every hour, but users report stale data. What is the most likely issue?

Accepted Answer

The refresh interval is too long. The most likely issue is that the refresh interval is too long. If the dashboard refreshes every hour but users are seeing stale data, the data source may update more frequently than the dashboard's refresh cycle, causing a lag between data changes and dashboard updates. This is a common scheduling mismatch in BI tools like Tableau or Power BI where the refresh interval must align with data source update frequency.

Answer

The dashboard is not published

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The dashboard uses cached data

Answer

The data source connection is broken

Question 3

A retail company wants to analyze customer purchase patterns over time. The data is stored in a relational database with tables for Customers, Orders, and Products. Which database concept should be used to ensure that each order references a valid customer?

Accepted Answer

Foreign key. A foreign key constraint enforces referential integrity by ensuring that every value in the 'customer_id' column of the Orders table matches a valid primary key value in the Customers table. This prevents orphaned records and guarantees that each order references an existing customer.

Answer

View

Answer

Index

Answer

Primary key

Question 4

A healthcare organization is subject to strict data privacy regulations requiring the classification of all data assets. The data governance team has identified three data sensitivity levels: Public, Internal, and Restricted. They have a new data pipeline importing patient health records from multiple clinics. The records include patient names, diagnoses, treatment codes, and insurance information. The team must ensure that the classification is applied correctly and that restricted data (e.g., diagnoses) is not exposed to unauthorized personnel. However, the pipeline uses automated tagging based on metadata rules, and some fields are misclassified. What is the most effective immediate action to improve classification accuracy?

Accepted Answer

Implement data loss prevention (DLP) tools that inspect content and enforce classification rules.. Implementing DLP tools with content inspection can automatically detect sensitive patterns (e.g., diagnosis codes) and enforce correct classification, directly addressing misclassification from incomplete metadata rules. Option A (encrypting all data) is a security measure but does not fix classification accuracy. Option B (manual review) is not scalable for a pipeline. Option C (expanding metadata rules) may help but is less effective since metadata can still miss patterns that DLP content inspection can catch.

Answer

Encrypt all data at rest and in transit regardless of classification.

Answer

Require manual review and reclassification of all incoming records.

Answer

Expand the metadata rule set to include more keywords and patterns.

Question 5

Which TWO of the following are benefits of database normalization to 3NF? (Select 2)

Accepted Answer

Reduces data redundancy. Normalization to 3NF eliminates transitive dependencies, which directly reduces data redundancy by ensuring each non-key attribute depends only on the primary key. This reduction in redundancy also increases data integrity because updates, inserts, and deletes are less likely to create inconsistencies or anomalies. In a relational database, 3NF achieves this without sacrificing the ability to reconstruct the original data via joins.

Answer

Improves query performance for all queries

Answer

Simplifies complex joins

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Eliminates all data anomalies

Question 6

An analyst needs to present quarterly sales data to the board. The CEO wants to see both overall trend and breakdown by region. Which dashboard layout is most effective?

Accepted Answer

A combination of a line chart for total and a stacked area chart for regional breakdown. It simultaneously satisfies the CEO's dual requirement: a line chart clearly shows the overall quarterly sales trend, while a stacked area chart breaks down total sales by region, allowing the board to see both the aggregate performance and the contribution of each region over time. This combination leverages the strengths of each chart type—line for trend clarity and stacked area for part-to-whole relationships—without overloading the viewer with data.

Answer

A single line chart with all regions

Answer

A KPI card with total sales

Answer

A table with all quarterly figures

Question 7

A data team is preparing a dashboard for executives. The team wants to highlight key performance indicators (KPIs) that are below target. Which of the following visualization techniques would most effectively draw attention to underperforming metrics without causing confusion?

Accepted Answer

Apply conditional formatting to turn KPI values red when below target.. Conditional formatting that turns KPI values red when below target is the most effective technique because it leverages pre-attentive visual processing — the human eye naturally notices color changes (especially red) before other visual elements. This allows executives to instantly identify underperforming metrics without needing to interpret complex chart types, reducing cognitive load and confusion.

Answer

Remove underperforming KPIs from the dashboard to avoid confusion.

Answer

Use a scatter plot to show the relationship between KPIs.

Answer

Use a pie chart showing the proportion of each KPI.

Question 8

A dataset contains a feature with values ranging from 10 to 1000. The analyst applies min-max normalization to scale the feature between 0 and 1. What is the normalized value of 520?

Accepted Answer

0.515. Min-max normalization formula: (x - min) / (max - min) = (520 - 10) / (1000 - 10) = 510 / 990 = 0.515.

Answer

0.510

Answer

0.480

Answer

0.520

Question 9

A large retail company is integrating customer data from two separate CRM systems into a new data warehouse. System A stores customer IDs as integers (e.g., 12345), while System B stores them as alphanumeric strings (e.g., 'CUST-12345-X'). Additionally, some customers exist in both systems but with slight name variations (e.g., 'John Smith' vs 'Jon Smith'). The data warehouse requires a unified customer table with a single unique identifier for each customer. The analyst needs to design the data acquisition process. Which of the following is the most appropriate first step?

Accepted Answer

Perform data profiling to analyze data distributions, data types, and quality issues in each source. Data profiling is the foundational first step in any data integration project. It systematically assesses source data types, formats, completeness, and quality issues (e.g., integer vs. alphanumeric IDs, name variations) before designing transformation logic. Without profiling, subsequent steps like fuzzy matching or ID standardization risk being built on incorrect assumptions about the data.

Answer

Use a simple crosswalk table based on exact name matches to link records

Answer

Load all data from both systems into a staging table, then run a fuzzy matching algorithm to identify duplicates

Answer

Standardize all customer IDs to a common format (e.g., UUIDs) and then merge the tables

Question 10

A data analyst needs to retrieve current weather data from a third-party service. The service provides an endpoint that returns data in JSON format over HTTP. Which data source type is being used?

Accepted Answer

API. The data analyst is retrieving data from a third-party service via an HTTP endpoint that returns JSON. This is the classic definition of an API (Application Programming Interface) — specifically a RESTful web API — which allows programmatic access to structured data over HTTP using standard methods like GET. The JSON format confirms it is an API response, not a file or stream.

Answer

Streaming data

Answer

Flat file

Answer

Web scraping

Question 11

A healthcare company's data analyst is tasked with presenting patient readmission rates to a group of doctors and nurses. The data shows that readmission rates are higher among patients with certain chronic conditions. The audience has limited data literacy, but they are familiar with clinical terms. The analyst wants to communicate the insights effectively and encourage discussion on preventive measures. The presentation will last 15 minutes, and the audience expects actionable insights. What should the analyst do?

Accepted Answer

Use a simple bar chart comparing readmission rates by condition.. A simple bar chart directly compares readmission rates across chronic conditions using a visual format that is intuitive for an audience with limited data literacy. It avoids overwhelming them with raw numbers or complex statistical outputs, enabling quick comprehension and fostering discussion on actionable preventive measures within the 15-minute timeframe.

Answer

Present a table of raw numbers for each condition.

Answer

Show a complex regression model output to demonstrate correlation.

Answer

Show a scatter plot of age vs. readmission rate.

Question 12

Refer to the exhibit. An ETL pipeline failed. What is the most likely root cause?

Accepted Answer

Network connectivity issues. The exhibit shows an ETL pipeline failure with a timeout error, which is a classic symptom of network connectivity issues. When the pipeline cannot reach the source or target system due to a network interruption, the process hangs until a timeout threshold is exceeded, causing the job to fail. This is the most likely root cause because timeouts are directly associated with network problems, not with data format, authentication, or storage issues.

Answer

Data format mismatch

Answer

Authentication failure

Answer

Insufficient disk space

Question 13

Refer to the exhibit. A data analyst is unable to run a query on the customers table after October 1, 2023. What is the reason?

Accepted Answer

The policy allows access only before October 1, 2023. The policy explicitly allows access only before October 1, 2023, meaning any query attempt on or after that date is denied. This is a time-based access control condition often implemented using a policy engine that checks the current time against a condition. Since the query fails after October 1, 2023, the policy's effective date restriction is the direct cause.

Answer

The resource name is incorrect

Answer

The action should be READ not SELECT

Answer

The policy denies access after October 1, 2023

Question 14

A data analyst creates a line chart showing monthly sales over the past year. The chart uses a y-axis starting at $100,000 instead of zero. What is the most likely misinterpretation a viewer might have?

Accepted Answer

The differences between months are exaggerated, making small changes look large.. Starting the y-axis at $100,000 instead of zero truncates the baseline, which visually exaggerates the relative differences between monthly sales values. This is a common data visualization pitfall that can mislead viewers into perceiving small fluctuations as significant trends, violating the principle of using a zero baseline for bar and line charts to accurately represent proportional change.

Answer

The sales appear to be decreasing when they are actually increasing.

Answer

The chart is correctly scaled, so no misinterpretation occurs.

Answer

The sales appear to be increasing when they are actually decreasing.

Question 15

A data analyst is working with a dataset that includes customer names, email addresses, and purchase history. The analyst wants to ensure that each customer is uniquely identified. Which TWO database concepts should be used to enforce uniqueness and link related data?

Accepted Answer

Foreign key. A primary key uniquely identifies each row in a table, ensuring no duplicate customer records. A foreign key links related data across tables by referencing the primary key of another table, enforcing referential integrity. Together, they guarantee uniqueness and enable relational joins between customer and purchase history tables.

Answer

Normalization

Answer

View

Answer

Index