This post is a part of the PL-300: Microsoft Power BI Data Analyst Exam Prep Hub; and this topic falls under these sections:
Model the data (25–30%)
   --> Create model calculations by using DAX
      --> Use Basic Statistical Functions

Below are 10 practice questions (with answers and explanations) for this topic of the exam.
There are also 2 practice tests for the PL-300 exam with 60 questions each (with answers) available on the hub.

Practice Questions

Question 1

Which DAX function returns the arithmetic mean of a numeric column?

A. MEDIAN
B. AVERAGEX
C. AVERAGE
D. MEAN

✅ Correct Answer: C

Explanation:
AVERAGE calculates the arithmetic mean of a numeric column. AVERAGEX is an iterator, and MEAN is not a valid DAX function.

Question 2

You need to count the number of unique customers in a sales table. Which function should you use?

A. COUNT
B. COUNTA
C. COUNTROWS
D. DISTINCTCOUNT

✅ Correct Answer: D

Explanation:
DISTINCTCOUNT counts unique values in a column, which is required when counting unique customers or products.

Question 3

What is the primary difference between COUNT and COUNTA?

A. COUNT works on tables; COUNTA works on columns
B. COUNT counts numeric values; COUNTA counts non-blank values of any type
C. COUNT ignores blanks; COUNTA counts blanks
D. COUNT is slower than COUNTA

✅ Correct Answer: B

Explanation:
COUNT counts only non-blank numeric values, while COUNTA counts all non-blank values regardless of data type.

Question 4

Which function should you use to count the number of rows returned by a table expression?

A. COUNT
B. COUNTA
C. COUNTROWS
D. DISTINCTCOUNT

✅ Correct Answer: C

Explanation:
COUNTROWS counts the number of rows in a table and is commonly used to count records after filters are applied.

Question 5

Which measure correctly calculates the median sales amount?

A.

Median Sales = MEDIANX(Sales, Sales[SalesAmount])

B.

Median Sales = MEDIAN(Sales[SalesAmount])

C.

Median Sales = AVERAGE(Sales[SalesAmount])

D.

Median Sales = SUM(Sales[SalesAmount])

✅ Correct Answer: B

Explanation:
MEDIAN calculates the middle value of a numeric column and is less sensitive to outliers than AVERAGE.

Question 6

Which function measures how spread out values are around the mean for an entire population?

A. VAR.S
B. VAR.P
C. STDEV.S
D. MEDIAN

✅ Correct Answer: B

Explanation:
VAR.P calculates population variance. VAR.S is used for samples.

Question 7

Which DAX function returns the population standard deviation?

A. STDEV.S
B. STDEVX.P
C. STDEV.P
D. VAR.P

✅ Correct Answer: C

Explanation:
STDEV.P calculates the standard deviation for an entire population dataset.

Question 8

You need to calculate the average sales amount only for products in the “Accessories” category. Which measure is correct?

A.

AVERAGE(Sales[SalesAmount], Product[Category] = "Accessories")

B.

CALCULATE(
    AVERAGE(Sales[SalesAmount]),
    Product[Category] = "Accessories"
)

C.

FILTER(
    AVERAGE(Sales[SalesAmount]),
    Product[Category] = "Accessories"
)

D.

AVERAGEX(
    Sales,
    Product[Category] = "Accessories"
)

✅ Correct Answer: B

Explanation:
CALCULATE modifies filter context, allowing the average to be evaluated only for the specified category.

Question 9

When should you prefer MEDIAN over AVERAGE?

A. When data has missing values
B. When performance is critical
C. When data contains outliers
D. When counting rows

✅ Correct Answer: C

Explanation:
The median is less affected by extreme values and provides a better measure of central tendency when outliers exist.

Question 10

Which statement about basic statistical measures is TRUE?

A. They should be created as calculated columns
B. They ignore filter context
C. They dynamically recalculate based on filters
D. They require a date table

✅ Correct Answer: C

Explanation:
Statistical measures are filter-context aware, meaning their results change dynamically based on slicers and filters.

Final PL-300 Exam Tips for Statistical Functions

• Know the differences between COUNT, COUNTA, COUNTROWS, and DISTINCTCOUNT
• Understand when to use MEDIAN vs AVERAGE
• Be comfortable with variance and standard deviation functions
• Expect filter context–based questions using CALCULATE
• Use measures, not calculated columns

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