Data Science Data Wrangling and Preprocessing 4

Question 1

Two rows have identical values across all columns. What wrangling step removes them?

Accepted Answer

Deduplication (drop_duplicates)

Answer

Dropping duplicates removes repeated rows that would otherwise bias counts and model training.

Question 2

A 'state' column contains 'CA', 'Ca', 'calif.', and 'California' for the same state. This is an example of what problem?

Accepted Answer

Inconsistent categorical values needing standardization

Answer

The same category written multiple ways must be standardized to a single canonical value before analysis.

Question 3

Using the IQR method, an outlier is typically a value beyond which boundary?

Accepted Answer

Below Q1 - 1.5*IQR or above Q3 + 1.5*IQR

Answer

The Tukey IQR rule flags points more than 1.5 times the interquartile range beyond the first or third quartile.

Question 4

You have monthly sales spread across 12 separate columns (Jan...Dec). Reshaping into a single 'month' column and 'sales' column is called what?

Accepted Answer

Melting / unpivoting to long format

Answer

Melting (unpivoting) converts wide-format columns into long-format key-value rows.

Question 5

Converting a continuous 'age' feature into groups like 'child', 'adult', 'senior' is known as what?

Accepted Answer

Binning (discretization)

Answer

Binning discretizes a continuous variable into a finite set of intervals or categories.

Data Science Practice Test