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Data Cleaning & Analysis
Data Cleaning & Analysis
Preparing data for accurate insights
What is Data Cleaning?
Process of fixing raw data
Removes errors and inconsistencies
Improves data quality
Essential before analysis
Why Data Cleaning Matters
Dirty data leads to wrong decisions
Inaccurate reports
Loss of trust in data
Business risks increase
Common Data Problems
Missing values
Duplicate records
Incorrect formats
Outliers
Missing Data
● Some fields may be empty
● Can affect analysis results
● Must be handled properly
● Depends on context
Handling Missing Values
Remove records
Replace with average
Replace with median
Mark as “Unknown”
Duplicate Data
Same record appears multiple times
Inflates counts
Distorts results
Must be removed
Removing Duplicates
Identify unique IDs
Compare multiple columns
Keep most accurate record
Use tools to automate
Data Standardization
Consistent formats
Same date structure
Same currency
Same naming conventions
Data Validation
Check value ranges
Ensure correct data types
Logical consistency checks
Improves reliability
Exploratory Data Analysis (EDA)
First step after cleaning
Understand patterns
Identify trends
Detect anomalies
Tools for Data Cleaning
Microsoft Excel
SQL queries
Python (Pandas)
Power BI
Analysis Techniques
Summary statistics
Trend analysis
Comparisons
Visual analysis
Business Impact
● Better decisions
● Accurate reports
● Improved forecasting
● Increased efficiency
Conclusion
● Cleaning is a critical step
● Analysis depends on clean data
● Good data = good insights
● Core skill for analysts