DA Data Analysis Tools and Programming 2

Question 1

What is the purpose of the pandas groupby() function?

Accepted Answer

Splitting data into groups and applying aggregate functions to each group

Answer

groupby() splits a DataFrame into groups based on one or more columns, then applies an aggregation function like sum or mean to each group.

Question 2

In Python, what does the NumPy function np.mean() calculate?

Accepted Answer

Arithmetic mean of array elements

Answer

np.mean() computes the arithmetic mean (average) of the elements in a NumPy array or along a specified axis.

Question 3

What is a Jupyter Notebook primarily used for?

Accepted Answer

Interactive data exploration combining code, output, and narrative text

Answer

Jupyter Notebooks allow analysts to write and run code in cells while embedding visualizations and explanatory text in a single document.

Question 4

What Excel function counts cells that meet a specific condition?

Accepted Answer

COUNTIF

Answer

COUNTIF counts the number of cells in a range that satisfy a given condition, such as counting all values above a threshold.

Question 5

What does df.isnull().sum() return in pandas?

Accepted Answer

Number of missing values per column

Answer

df.isnull().sum() counts the number of NaN (missing) values in each column of the DataFrame.

DA - Data Analyst Practice Test