StudyToCert

All certifications / Data+ / Lessons

CompTIA Data+ DA0-002 · Domain 2: Data acquisition and preparation

Data quality problems: duplicates, missing values, invalid values, outliers, inconsistent formats and redundancy

▶ Watch the overview video

Last reviewed September 25, 2026 · Leer en español

Analysts often say most of their time goes into cleaning data. That is because raw data from real systems is messy, and conclusions drawn from dirty data are wrong no matter how good the analysis is. Data+ expects you to recognize each common problem and its usual fix.

Free account

Keep reading for free

Create a free StudyToCert account to read the rest of this lesson: 6 more sections, 4 key terms, a real-world example, an exam tip and self-check questions. Every lesson, lab and practice test is free with an account.

Sign up free Log in

Study Data+ for free
A week-by-week plan with every lesson, quizzes, checkpoint tests, a practice exam and hands-on labs.
Open the Data+ study plan