Data Science with Python Certification Data Science with Python Exploratory Data Analysis 3

Question 1

What does a Pearson correlation coefficient of -0.95 between two variables indicate?

Accepted Answer

A strong negative linear relationship

Answer

A value close to -1 indicates a strong negative linear relationship where one variable increases as the other decreases.

Question 2

Which pandas function is used to reshape a DataFrame from wide format to long format?

Accepted Answer

pd.melt()

Answer

pd.melt() unpivots a DataFrame from wide to long format by converting column headers into row values.

Question 3

In EDA, what does a KDE (Kernel Density Estimate) plot show?

Accepted Answer

A smoothed continuous estimate of the probability density function

Answer

A KDE plot estimates the probability density of a continuous variable by smoothing the data using a kernel function.

Question 4

What is the effect of calling df.fillna(df.mean()) on a DataFrame with missing numeric values?

Accepted Answer

Replaces NaN in each column with that column's mean value

Answer

df.mean() computes a per-column mean Series, and fillna() replaces each column's NaN values with its own mean.

Question 5

Which of the following best describes a violin plot in EDA?

Accepted Answer

A combination of a box plot and a KDE that shows distribution shape

Answer

A violin plot mirrors the KDE on both sides of a central axis while embedding a mini box plot to show quartiles and median.

Data Science with Python Certification Practice Test