Data cleaning, merging, SQL queries, ETL and transformation methods, outliers and data quality issues.
40 cards · basic cards · AI-written, checked twice. Edit anything.
- What is the primary purpose of data cleaning?
Show answer
To ensure data is accurate, complete, and consistent for analysis- Name three common steps in the data cleaning process.
Show answer
Removing duplicates, handling missing values, and correcting inconsistent formats- What does deduplication mean in data cleaning?
Show answer
Removing duplicate rows or records that represent the same entity- What is whitespace trimming used for?
Show answer
Removing leading and trailing spaces from text fields- In data cleaning, what is a NULL value?
Show answer
A missing or absent value in a data field- What are three ways to handle missing values in a dataset?
Show answer
Delete rows with missing values, fill with mean/median/mode, or use imputation- What is data validation in the context of data cleaning?
Show answer
Checking that data conforms to required format, type, and value constraints- What is data transformation?
Show answer
Converting data from one format or structure into another suitable for analysis- What is an outlier in a dataset?
Show answer
A data point that is significantly different from other observations- How can Z-score be used to identify outliers?
Show answer
Values with absolute Z-score greater than 3 are typically considered outliers- What is the Interquartile Range (IQR) method for detecting outliers?
Show answer
Points below Q1 minus 1.5 times IQR or above Q3 plus 1.5 times IQR are outliers- What is data consistency?
Show answer
Ensuring that data values are uniform in format and do not conflict across the dataset- What does data accuracy mean?
Show answer
Data correctly represents the true value of what it is measuring- What is data completeness?
Show answer
All required data fields contain values with no missing entries- What does an INNER JOIN return?
Show answer
Only rows where the join condition is true in both tables
FlashKeepers