DA0-002 Practice Test 14 — 15 Questions

Question 1

A data analyst wants to show the relative proportions of defects by type in a manufacturing process. There are 6 defect types. Which chart is most appropriate?

Accepted Answer

Pie chart. A pie chart is standard for showing parts of a whole, especially with few categories. Bar chart is also possible but not the best for proportions. Scatter and line charts are not for proportions.

Answer

Line chart

Answer

Stacked bar chart

Answer

Scatter plot

Question 2

A data engineer is designing a data pipeline to ingest streaming data from IoT sensors. The sensors send data every second, and the pipeline must handle bursts of up to 10,000 messages per second. Which approach is most appropriate for capturing this data before processing?

Accepted Answer

Use a message queue to buffer the incoming data. A message queue (e.g., Apache Kafka, Amazon Kinesis, or RabbitMQ) provides an asynchronous buffer that decouples the high-velocity ingestion (up to 10,000 messages/second) from downstream processing. This allows the pipeline to absorb burst traffic without overwhelming the processing layer, ensures data durability, and supports replayability in case of failures.

Answer

Directly write each message to a relational database

Answer

Load directly into a data warehouse

Answer

Store data in flat files and process in nightly batches

Question 3

A data analyst is examining the relationship between advertising spend (in thousands) and sales (in thousands). The Pearson correlation coefficient is computed as r = -0.85. Which of the following interpretations is correct?

Accepted Answer

There is a strong negative linear relationship.. Pearson r measures linear correlation: -0.85 indicates a strong negative linear relationship (as one increases, the other decreases). The magnitude |0.85| is close to 1, so strong.

Answer

There is no linear relationship.

Answer

There is a strong positive linear relationship between advertising spend and sales.

Answer

There is a weak negative linear relationship.

Question 4

An analyst is using SQL to analyze employee data. Which THREE of the following are valid uses of the WHERE clause? (Select three.)

Accepted Answer

Filter rows where manager_id is NULL using IS NULL. WHERE can filter using LIKE, BETWEEN, and IS NULL. HAVING is for aggregated results, and ORDER BY is for sorting.

Answer

Sort the result set by hire_date

Answer

Filter groups after aggregation using HAVING

Question 5

A data analyst is using the IQR method to identify outliers in a dataset. The first quartile (Q1) is 25 and the third quartile (Q3) is 45. What is the upper bound for identifying outliers?

Accepted Answer

75. Upper bound = Q3 + 1.5 * IQR; IQR = Q3 - Q1 = 20; 1.5*20 = 30; 45+30 = 75.

Answer

85

Answer

65

Answer

55

Question 6

A dataset contains a column 'Income' with values in different scales (some in thousands, some in hundreds). What is the best way to standardize this column for use in a machine learning model?

Accepted Answer

Apply standard scaling (Z-score normalization). Standard scaling (Z-score normalization) is the best approach because it transforms the data to have a mean of 0 and a standard deviation of 1, making values on different scales (thousands vs hundreds) directly comparable. Min-max scaling also rescales to [0,1], but it is sensitive to outliers and does not handle different scales as effectively when the distribution is not uniform. Log transformation is for reducing skewness, not for standardizing scales. Removing the column discards useful information.

Answer

Apply min-max scaling to range [0,1]

Answer

Apply log transformation

Answer

Remove the column

Question 7

A data analyst wants to concatenate first_name and last_name columns with a space in between. Which string function combination should be used in SQL?

Accepted Answer

CONCAT(first_name, ' ', last_name). CONCAT joins strings; adding a space produces 'First Last'.

Answer

first_name + ' ' + last_name

Answer

SUBSTRING(first_name, 1, 1) + '.' + last_name

Answer

CONCAT(first_name, last_name)

Question 8

A data analyst is performing data profiling on a customer table. Which metric would best help identify missing values in the 'phone' column?

Accepted Answer

Null count. Null count directly measures missing values.

Answer

Cardinality

Answer

Mean

Answer

Row count

Question 9

A data analyst is validating referential integrity between orders and customers tables. Which TWO of the following checks should the analyst perform?

Accepted Answer

Check that no customer is deleted while having orders. Referential integrity ensures foreign keys match primary keys and no orphaned records.

Answer

Check that every order has a non-null order_id

Answer

Check that customer names are unique

Answer

Check that order amounts are positive

Question 10

Drag and drop the steps to normalize a database table from 1NF to 3NF in the correct order.

Accepted Answer

Step 1: Achieve 1NF by removing repeating groups and ensuring atomic values. Step 2: Achieve 2NF by removing partial dependencies. Step 3: Achieve 3NF by removing transitive dependencies.. Normalization proceeds from 1NF to 2NF to 3NF, then table creation and foreign keys.

Answer

Step 1: Achieve 3NF by removing transitive dependencies. Step 2: Achieve 2NF by removing partial dependencies. Step 3: Achieve 1NF by removing repeating groups.

Answer

Step 1: Achieve 2NF by removing partial dependencies. Step 2: Achieve 1NF by removing repeating groups. Step 3: Achieve 3NF by removing transitive dependencies.

Answer

Step 1: Achieve 1NF by removing repeating groups. Step 2: Achieve 3NF by removing transitive dependencies. Step 3: Achieve 2NF by removing partial dependencies.

Question 11

An analyst needs to count the number of orders per customer but only for customers who have placed more than 5 orders. Which SQL construct allows filtering after aggregation?

Accepted Answer

HAVING COUNT(*) > 5. HAVING is used to filter groups based on aggregate conditions, unlike WHERE which filters before aggregation.

Answer

WHERE COUNT(*) > 5

Answer

LIMIT 5

Answer

ORDER BY COUNT(*) > 5

Question 12

An analyst is performing EDA and wants to measure the strength and direction of linear relationship between two continuous variables. Which statistical measure should they compute?

Accepted Answer

Correlation. Correlation coefficient (Pearson's r) measures linear relationship strength and direction.

Answer

Standard deviation

Answer

Mean

Answer

Mode

Question 13

A data analyst is using a window function to assign a unique rank to each employee within their department based on salary, with ties receiving the same rank and leaving gaps. Which function should be used?

Accepted Answer

RANK(). RANK() assigns the same rank to ties and leaves gaps (e.g., 1,1,3). DENSE_RANK() does not leave gaps.

Answer

DENSE_RANK()

Answer

ROW_NUMBER()

Answer

NTILE()

Question 14

You are a data analyst at a retail company. Your team has deployed a new dashboard that displays real-time inventory levels across all warehouses. The dashboard uses a traffic light color scheme (green = sufficient, yellow = low, red = out of stock). After one week, the warehouse managers complain that the dashboard is overwhelming because it shows all 500+ products at once, and they cannot quickly identify which items need immediate attention. They request a way to prioritize items that are red or yellow. Additionally, the dashboard updates every second, causing the screen to flicker constantly, which they find distracting. You need to redesign the dashboard to address these issues. Which course of action should you take?

Accepted Answer

Add a filter to show only items with red or yellow status, and reduce the refresh rate to every 5 minutes.. It directly addresses both user complaints: adding a filter to show only red/yellow items reduces cognitive overload by hiding the 500+ products that are not critical, and reducing the refresh rate from every second to every 5 minutes eliminates distracting screen flicker while still providing near-real-time inventory updates. This approach balances usability with the need for timely alerts without overwhelming the user.

Answer

Replace the dashboard with a static table that shows all products sorted alphabetically, and increase the refresh rate to every 2 seconds.

Answer

Remove the color scheme and display only numerical values, and keep the refresh rate at 1 second.

Answer

Add additional colors to distinguish more inventory levels and increase the refresh rate to every 500 milliseconds.

Question 15

A data analyst wants to use a Z-score to standardize a dataset. The variable has a mean of 50 and a standard deviation of 10. What is the Z-score for a raw value of 70?

Accepted Answer

2. Z = (X - mean) / std = (70 - 50) / 10 = 2.

Answer

0.5

Answer

20

Answer

-2