DA Data Cleaning and Preparation 3

Question 1

What is a left join imputation strategy?

Accepted Answer

Filling NULLs from a reference lookup table via a left join

Answer

Removing rows with missing values

Answer

Replacing NULLs with column averages

Answer

Using linear regression to predict missing values

Question 2

What is the difference between structured and unstructured data?

Accepted Answer

Structured data fits in predefined rows/columns; unstructured data lacks a fixed schema

Answer

Structured data is large; unstructured is small

Answer

Unstructured data is always numeric; structured is text

Answer

There is no meaningful difference for data analysts

Question 3

What is the purpose of a data dictionary?

Accepted Answer

Documenting the definitions, data types, and relationships of dataset fields

Answer

Translating data between languages

Answer

Storing raw data backups

Answer

Encrypting column values

Question 4

What is the risk of removing rows with missing values (listwise deletion)?

Accepted Answer

It can introduce bias if missing data is not random

Answer

It makes the dataset too large

Answer

It always improves model accuracy

Answer

It converts categorical to numeric data

Question 5

What is data reshaping in pandas (Python)?

Accepted Answer

Converting data between wide and long formats using melt or pivot

Answer

Changing column data types

Answer

Removing duplicate rows

Answer

Sorting values by index

Question 6

Which of the following is a sign of low-quality data?

Accepted Answer

High percentage of NULL values in critical fields

Answer

High row count

Answer

Consistent date formats across columns

Answer

Unique primary key values