Data Analysis Tools and Programming Flashcards
6 cards from real DA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Data Analysis Tools and Programming flashcards as text
What is the purpose of the pandas groupby() function?
Answer: Splitting data into groups and applying aggregate functions to each group
groupby() splits a DataFrame into groups based on one or more columns, then applies an aggregation function like sum or mean to each group.
In Python, what does the NumPy function np.mean() calculate?
Answer: Arithmetic mean of array elements
np.mean() computes the arithmetic mean (average) of the elements in a NumPy array or along a specified axis.
What is a Jupyter Notebook primarily used for?
Answer: Interactive data exploration combining code, output, and narrative text
Jupyter Notebooks allow analysts to write and run code in cells while embedding visualizations and explanatory text in a single document.
What Excel function counts cells that meet a specific condition?
Answer: COUNTIF
COUNTIF counts the number of cells in a range that satisfy a given condition, such as counting all values above a threshold.
What does df.isnull().sum() return in pandas?
Answer: Number of missing values per column
df.isnull().sum() counts the number of NaN (missing) values in each column of the DataFrame.
What is the purpose of the pd.merge() function in pandas?
Answer: Combine two DataFrames based on a common key column, similar to a SQL JOIN
pd.merge() joins two DataFrames on one or more key columns, supporting inner, left, right, and outer joins.