PL-300 Visualize and analyze the data Practice Question
This PL-300 practice question tests your understanding of visualize and analyze the data. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A Power BI report uses a measure that calculates Year-over-Year sales growth. Users report that the measure shows incorrect values for January 2024 when compared to January 2023. The data model contains a Date table with a continuous date range from January 1, 2020 to December 31, 2024. Which DAX function is most likely causing the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Why wrong: PARALLELPERIOD shifts a set of dates forward or backward but requires a full period; it is less commonly used for simple YoY comparisons.
B
DATEADD
Why wrong: DATEADD is commonly used for YoY comparisons and can work correctly if the date range is continuous. It is not the most likely cause here.
C
SAMEPERIODLASTYEAR
SAMEPERIODLASTYEAR is the most likely cause because it returns the same period from the previous year, but if the Date table lacks data for the entire previous period, it can produce incorrect results for month-over-month comparisons.
D
PREVIOUSYEAR
Why wrong: PREVIOUSYEAR returns the whole previous year, which may cause incorrect comparisons when filtering by a specific month.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SAMEPERIODLASTYEAR
SAMEPERIODLASTYEAR is the most likely cause of the issue because it returns a set of dates from the previous year that exactly matches the current period's date range. For January 2024, it will return January 1–31, 2023, but if the Date table does not have a full contiguous range (e.g., missing weekends or holidays), or if the measure relies on a different granularity, the comparison may produce incorrect values. The other functions shift dates differently or return entire periods, which can cause mismatches in Year-over-Year calculations.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
PARALLELPERIOD
Why it's wrong here
PARALLELPERIOD shifts a set of dates forward or backward but requires a full period; it is less commonly used for simple YoY comparisons.
✗
DATEADD
Why it's wrong here
DATEADD is commonly used for YoY comparisons and can work correctly if the date range is continuous. It is not the most likely cause here.
✓
SAMEPERIODLASTYEAR
Why this is correct
SAMEPERIODLASTYEAR is the most likely cause because it returns the same period from the previous year, but if the Date table lacks data for the entire previous period, it can produce incorrect results for month-over-month comparisons.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
PREVIOUSYEAR
Why it's wrong here
PREVIOUSYEAR returns the whole previous year, which may cause incorrect comparisons when filtering by a specific month.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse SAMEPERIODLASTYEAR with DATEADD or PARALLELPERIOD, not realizing that SAMEPERIODLASTYEAR returns the exact same relative dates (e.g., same day numbers) while DATEADD shifts by an interval and PARALLELPERIOD returns full periods, making SAMEPERIODLASTYEAR the correct choice for precise Year-over-Year comparisons when the Date table is continuous.
Detailed technical explanation
How to think about this question
Under the hood, SAMEPERIODLASTYEAR uses the existing filter context to find the exact same set of dates shifted back one year, relying on the Date table's contiguous range. A subtle behavior is that if the Date table has missing dates (e.g., non-trading days), the function may return fewer dates than expected, causing incorrect aggregations. In real-world scenarios, this often manifests when comparing months with different numbers of trading days or when the Date table is not marked as a date table, leading to unexpected results in time intelligence calculations.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Visualize and analyze the data — This question tests Visualize and analyze the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SAMEPERIODLASTYEAR — SAMEPERIODLASTYEAR is the most likely cause of the issue because it returns a set of dates from the previous year that exactly matches the current period's date range. For January 2024, it will return January 1–31, 2023, but if the Date table does not have a full contiguous range (e.g., missing weekends or holidays), or if the measure relies on a different granularity, the comparison may produce incorrect values. The other functions shift dates differently or return entire periods, which can cause mismatches in Year-over-Year calculations.
What should I do if I get this PL-300 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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