DA0-002 Practice Test 5 — 25 Questions

Question 1

A company uses a dashboard to monitor server uptime. The data is collected every minute, but the dashboard only refreshes every hour. Users see gaps in the line chart. What is the most likely cause, and how should it be fixed?

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

Accepted Answer

Increase the dashboard refresh rate to match data collection frequency. The dashboard refreshes hourly while data arrives every minute, so between refreshes the chart shows only the last-fetched snapshot and appears to have gaps or stale segments. Aligning the dashboard refresh interval with the data collection frequency (or at least much closer to it) ensures the chart reflects the continuous stream of one-minute data points.

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The line chart should interpolate missing data points

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Switch to a bar chart to avoid gaps

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Use a different data series with the same refresh rate

Question 2

A data analyst is creating a dashboard and wants to maximize the data-ink ratio. Which action supports this principle?

Accepted Answer

Removing gridlines and reducing chart borders.. Removing unnecessary gridlines and decorative elements reduces non-data ink, thereby increasing the data-ink ratio. The data-ink ratio is the proportion of ink used to display data versus total ink used in the chart.

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Including detailed data tables alongside charts.

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Using 3D effects to make bars stand out.

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Adding a background image to make the dashboard visually appealing.

Question 3

A time series of monthly sales data exhibits a clear upward trend over several years, with consistent peaks each December. Which components are present in this series?

Accepted Answer

Trend and seasonality. The time series exhibits an upward trend over several years and consistent peaks each December, which is seasonality. Therefore, the components present are trend and seasonality. Cyclical components are not mentioned, and irregular components are always present but not the focus.

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Cyclical and irregular components only

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Seasonality and cyclical components only

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Trend and irregular components only

Question 4

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 scales values using the formula (x - min) / (max - min). With min=10 and max=1000, the normalized value of 520 is (520 - 10) / (1000 - 10) = 510 / 990 = 0.51515..., which rounds to 0.515. Option A correctly applies this formula.

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0.510

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0.480

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0.520

Question 5

A business analyst wants to compare the proportion of total sales contributed by each product category in the current year. Which visualization is most suitable?

Accepted Answer

Pie chart. A pie chart is designed to show how a whole is divided into proportional parts, making it the natural fit for comparing each product category's share of total sales. Each slice's angle directly encodes the category's percentage contribution, which is exactly what the analyst needs. For a single-period composition question, pie charts communicate proportions intuitively.

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Scatter plot

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Line chart

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Histogram

Question 6

A data architect needs to store raw data from various sources, including social media feeds and log files, for future analysis. The data may be used for machine learning and ad-hoc queries. Which storage solution is most appropriate for storing raw data in its native format?

Accepted Answer

Data lake. A data lake is designed to store raw data in its native format, including unstructured and semi-structured data from sources like social media feeds and log files. It supports schema-on-read, making it ideal for future machine learning and ad-hoc queries without requiring upfront transformation. This aligns directly with the requirement to preserve raw data for flexible analysis.

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Data mart

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Relational database

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Data warehouse

Question 7

A government agency's data analyst is commissioned to produce a report on public transportation usage trends. The report will be read by policymakers, transit planners, and the general public. The data includes ridership numbers, delay rates, and demographic breakdowns. The analyst needs to ensure the report is accessible and persuasive, especially to non-technical readers. The goal is to advocate for increased funding in underserved areas. The report must be data-driven but also tell a compelling story. What strategy should the analyst prioritize?

Accepted Answer

Create a narrative that highlights the impact of delayed trains on low-income commuters.. It directly addresses the need to make data accessible and persuasive to non-technical readers by weaving a narrative around a specific, relatable impact (delayed trains on low-income commuters). This approach aligns with the goal of advocating for increased funding in underserved areas, as it humanizes the data and creates a compelling story that policymakers and the public can understand and act upon, without requiring technical expertise.

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Provide raw data in appendices only.

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Use complex statistical analysis to show significance of trends.

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Focus solely on ridership numbers without context.

Question 8

A data analyst needs to combine customer information from a CRM table and order information from an orders table, returning only customers who have placed at least one order. Which type of join should the analyst use?

Accepted Answer

INNER JOIN. An INNER JOIN between the CRM table and the orders table returns only rows where there is a match in both tables based on the join key (e.g., customer ID). This satisfies the requirement to return only customers who have placed at least one order, because any customer without an order in the orders table will be excluded from the result set.

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RIGHT JOIN

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FULL OUTER JOIN

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LEFT JOIN

Question 9

A retailer wants to test if a new website layout increases the average time spent on the site. They split traffic: control group (old layout) and treatment group (new layout). Which statistical test is most appropriate to compare the average time spent between the two groups?

Accepted Answer

Two-sample t-test. The question compares the means of a continuous outcome (average time spent) between two independent groups (control vs. treatment), which is exactly the two-sample t-test's purpose. The two-sample t-test evaluates whether the difference in group means is statistically significant, assuming approximately normal distributions or sufficiently large samples. It is the standard test for a two-group A/B comparison on a continuous metric.

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ANOVA

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Pearson correlation

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Chi-square test

Question 10

When designing a dashboard for executives, which principle is most important to follow to ensure key information is immediately visible?

Accepted Answer

Create a visual hierarchy with the most important metric prominently displayed.. Visual hierarchy places the most important metric in the prime viewing position (typically top-left or center-top) with the largest size and strongest contrast, so an executive scanning for five seconds immediately sees the headline number. This is the defining principle of executive dashboard design because executives consume dashboards in brief, infrequent glances rather than deep analytical sessions.

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Apply consistent color coding across all charts.

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Use as many colors as possible to highlight different data points.

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Include all available data to provide complete context.

Question 11

A data analyst needs to combine customer data from two tables: Customers (CustomerID, Name) and Orders (OrderID, CustomerID, Amount). Only customers who have placed at least one order should be included. Which JOIN type should be used?

Accepted Answer

INNER JOIN. An INNER JOIN returns only rows where there is a match in both tables. Since the requirement is to include only customers who have placed at least one order, the INNER JOIN on CustomerID will filter out any customer without a matching order record, exactly meeting the condition.

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LEFT JOIN

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FULL OUTER JOIN

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RIGHT JOIN

Question 12

A data analyst runs an A/B test on a new website layout. The test yields a p-value of 0.04 with the null hypothesis being no difference in conversion rates. The significance threshold is α=0.05. Which of the following is the correct conclusion?

Accepted Answer

Reject the null hypothesis; there is a statistically significant difference in conversion rates.. Since p-value (0.04) < α (0.05), we reject the null hypothesis and conclude there is a statistically significant difference. However, statistical significance does not guarantee practical significance.

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The result is not significant; accept the alternative hypothesis.

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Reject the null hypothesis; the new layout is proven to increase conversions.

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Fail to reject the null hypothesis; there is no evidence of a difference.

Question 13

A business intelligence analyst is designing a dashboard for executives. The dashboard includes revenue, profit margin, and customer satisfaction score. To maximize the data-ink ratio, the analyst should:

Accepted Answer

Remove gridlines, use minimal colors, and avoid decorative elements. Maximizing the data-ink ratio means every drop of ink should convey data, so removing gridlines, minimizing color, and stripping decorative elements directly increases the proportion of ink devoted to actual data. This aligns with Edward Tufte's principle that non-data ink and redundant ink should be eliminated or minimized. Executives need fast, clear signal, so a clean chart with minimal chrome communicates revenue, margin, and CSAT more effectively.

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Add a background image of the company logo

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Use different font styles for each metric label

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Use 3D pie charts with shadow effects

Question 14

Refer to the exhibit. A data analyst is troubleshooting a failed dashboard refresh. The error log shows repeated SQL syntax errors. Which of the following is the most likely cause?

Accepted Answer

The query contains a syntax mistake.. The error log explicitly states 'repeated SQL syntax errors,' which directly indicates that the SQL query being executed is malformed. A syntax mistake in the query (e.g., missing keyword, incorrect clause order, or mismatched parentheses) will cause the database to reject the statement before any execution begins, leading to the exact error described.

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The database server is offline.

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The user does not have permissions to access the table.

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The network connection timed out.

Question 15

A data analyst is cleaning a dataset and finds that some cells in the 'email' column contain leading spaces. Which string function should be used to remove these spaces?

Accepted Answer

TRIM. The TRIM function removes leading and trailing spaces (and sometimes other whitespace) from a string, which directly addresses the leading spaces in the email column. In most SQL dialects and data tools, TRIM is the standard function for stripping both leading and trailing spaces, making it the correct choice for cleaning the data.

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LTRIM

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REPLACE

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SUBSTRING

Question 16

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.

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Key-value store; create a secondary index on category

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Graph database; create a relationship between products

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Wide-column store; create a column family for category

Question 17

An analyst is conducting an A/B test to compare two website designs. The null hypothesis is that there is no difference in conversion rates. The p-value obtained is 0.03, and the significance threshold is 0.05. What should the analyst conclude?

Accepted Answer

Reject the null hypothesis; there is a significant difference.. In hypothesis testing, if the p-value (0.03) is less than the significance level (0.05), you reject the null hypothesis. This indicates that there is statistically significant evidence of a difference in conversion rates between the two designs. The correct conclusion is to reject the null hypothesis.

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Accept the alternative hypothesis that the new design is better.

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The test is inconclusive; need a larger sample size.

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Fail to reject the null hypothesis; there is no significant difference.

Question 18

A data analyst is creating a report to compare the performance of sales regions across multiple years. The report will be used by regional managers to identify trends. Which visualization approach best supports this?

Accepted Answer

Small multiples of line charts, one per region. Small multiples of line charts, one per region, allow regional managers to easily compare trends across years without visual clutter. Each region gets its own chart with consistent axes, making patterns and outliers clear. This approach supports the goal of identifying trends per region while enabling cross-region comparison.

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A single line chart with all regions overlaid

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A bar chart with years on x-axis and regions as grouped bars

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A stacked area chart with all regions

Question 19

A retail company wants to identify customer segments based on purchase history and demographics. Which technique is most appropriate for this task?

Accepted Answer

K-means clustering. K-means clustering is an unsupervised learning algorithm that partitions observations into k groups based on similarity across multiple features, making it ideal for segmenting customers by purchase history and demographics. It doesn't require labeled outcomes, which matches the exploratory nature of customer segmentation. The algorithm iteratively assigns points to the nearest centroid and recalculates centroids until convergence.

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Linear regression

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Chi-square test

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Logistic regression

Question 20

A data analyst wants to compare the revenue across five different product categories. Which chart type is best suited?

Accepted Answer

Bar chart. A bar chart is the best choice for comparing a categorical variable (five product categories) against a quantitative measure (revenue). Each category gets its own bar, making relative magnitudes easy to compare side by side. Bar charts handle a small number of discrete categories cleanly, which matches this scenario exactly.

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Scatter plot

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Pie chart

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Line chart