DA0-002 Data Acquisition and Preparation Practice Question
In a dataset of employee salaries, the analyst notices one value that is significantly higher than the rest. Using the IQR method, which values are typically considered outliers?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Values beyond Q1 - 1.5*IQR or Q3 + 1.5*IQR
Outliers are values less than Q1 - 1.5*IQR or greater than Q3 + 1.5*IQR.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Values beyond Q1 - 3*IQR or Q3 + 3*IQR
Why it's wrong here
The IQR method flags outliers beyond Q1 - 1.5*IQR or Q3 + 1.5*IQR; the 3*IQR multiplier describes extreme outliers, not the standard threshold. The 1.5 multiplier is the conventional Tukey fence applied to salary distributions.
- ✓
Values beyond Q1 - 1.5*IQR or Q3 + 1.5*IQR
Why this is correct
Values falling below Q1 − 1.5×IQR or above Q3 + 1.5×IQR are flagged as outliers, satisfying the stem's requirement to identify the salary that sits significantly higher than the rest. Tukey's fences define this boundary, so an extreme high salary exceeding Q3 + 1.5×IQR is correctly detected.
- ✗
Values beyond mean ± 2 standard deviations
Why it's wrong here
Mean ± 2 standard deviations is a z-score heuristic assuming normality, not the IQR method. IQR fences sit at Q1 - 1.5*IQR and Q3 + 1.5*IQR, derived from quartiles and resistant to the very extreme salary values being detected.
- ✗
Values beyond min and max
Why it's wrong here
Minimum and maximum are the dataset's extremes, so nothing can fall beyond them; this defines the range, not an outlier boundary. The IQR method places fences at Q1 - 1.5*IQR and Q3 + 1.5*IQR, which can sit inside the observed min and max.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DA0-002 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DA0-002 exam.