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Data Science Course ( Interview Questions ) Exam

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Data Science Course ( Interview Questions ) Exam

Welcome to your ultimate Data Analytics & Data Science Interview Questions Prep!

This page is designed to help you practice and master the most important interview questions from Python, Pandas, NumPy, SQL, and Power BI. Whether you’re preparing for your first analytics role or aiming for a data science career upgrade, these carefully selected MCQs and scenario-based questions will sharpen your problem-solving skills and boost your confidence for real interviews.

Name

Email

Course

Phone

Which of the following is used to handle missing values in Python?

Deselect Answer

dropna()

fillna()

Both a and b

None of the above

None

Which attribute shows the number of rows and columns in Pandas?

Deselect Answer

df.shape

df.size

df.dimension

df.length

None

In Pandas, which function is used to read a CSV file?

Deselect Answer

pd.csv_read()

pd.read_csv()

pd.load_csv()

pd.read()

None

Which of the following is NOT a visualization in Power BI?

Deselect Answer

TreeMap

Matrix

Bar chart

Heatmap

None

What is the output of bool([])?

Deselect Answer

Error

False

None

True

None

What is the output of sorted([3,1,2])?

Deselect Answer

None

Error

[3,2,1]

[1,2,3]

None

Which method gives the first 5 rows of a DataFrame?

Deselect Answer

df.head()

df.top()

df.first()

df.tail()

None

Which function is used to merge two DataFrames?

Deselect Answer

pd.concat()

All of the above

pd.merge()

pd.join()

None

What will df['col1'].unique() return?

Deselect Answer

Count of unique values

None

Index of unique rows

Unique values in column

None

Which Pandas function is used to combine DataFrames vertically?

Deselect Answer

pd.concat()

pd.append()

pd.merge()

pd.join()

None

In Power BI, which type of join is used by default in relationships?

Deselect Answer

Right Join

Full Join

Inner Join

Left Join

None

NumPy (Conditional Replacement) You have a 2D NumPy array. You want to replace all negative numbers with 0, but only for rows where the row sum is negative. Which is correct? 5 Marks

Deselect Answer

arr[arr < 0] = 0

arr[np.sum(arr, axis=1) < 0] = np.where(arr[np.sum(arr, axis=1) < 0] < 0, 0, arr[np.sum(arr, axis=1) < 0])

arr[np.sum(arr, axis=1) < 0] = np.clip(arr, 0, None)

Use nested for loops

None

Which method writes a DataFrame to Excel?

Deselect Answer

df.to_csv()

df.to_excel()

df.save_excel()

df.write_excel()

None

Which of the following creates an array of zeros in NumPy?

Deselect Answer

np.zeros()

np.empty()

np.ones()

np.array(0)

None

Which of the following is NOT a data visualization library in Python?

Deselect Answer

Seaborn

Matplotlib

ggplot2

Plotly

None

What is the output of len(set([1,2,2,3,3,3]))?

Deselect Answer

1

6

2

3

None

Python (Frequency Count) You have a list of numbers with millions of elements. Which method is the most efficient way to find the top 3 most frequent numbers? 5 Marks

Deselect Answer

Use collections.Counter().most_common(3)

Sort the list and take first 3 values

Use list.count() in a loop

Convert to Pandas DataFrame and use value_counts()

None

Which data type does range(5) return in Python 3?

Deselect Answer

list

range object

tuple

array

None

What does len("Data Science") return?

Deselect Answer

10

13

11

12

None

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

Deselect Answer

Removes null values

Fills null values with 0

Counts null values per column

Deletes null columns

None

Which keyword is used to define a function in Python?

Deselect Answer

function

def

define

fun

None

Which of the following is mutable in Python?

Deselect Answer

Integer

List

String

Tuple

None

Which language is used in Power BI for data modeling?

Deselect Answer

DAX

Python

SQL

R

None

What will print(type(lambda x: x+1)) return?

Deselect Answer

Error

None

In SQL, which clause is used to filter aggregated results?

Deselect Answer

HAVING

WHERE

ORDER BY

GROUP BY

None

Pandas (Handling Missing Values) You want to replace missing values in some columns with the mean and in others with the mode. Which Pandas approach is most efficient? 5 Marks

Deselect Answer

Use df.fillna(df.mean()) for all columns

Use SQL inside Pandas with pd.read_sql()

Apply df.apply(lambda x: x.fillna(x.mean()) if x.dtype!='object' else x.fillna(x.mode()[0]))

Loop through each column with for and apply fillna()

None

Which of the following is NOT a step in the data analysis process?

Deselect Answer

Model Training

Data Collection

Data Degradation

Data Cleaning

None

What type of data is the number of students in a class?

Deselect Answer

Ordinal

Categorical

Discrete

Continuous

None

Which SQL keyword is used to remove duplicate values from a result set?

Deselect Answer

HAVING

DISTINCT

UNIQUE

GROUP BY

None

Which module in Python is used for regular expressions?

Deselect Answer

regex

pattern

re

string

None

Which method sorts values in Pandas DataFrame?

Deselect Answer

df.sort_index()

None

Both a and b

df.sort_values()

None

Which of the following SQL queries retrieves all students with marks greater than 80?

Deselect Answer

SELECT * FROM students GROUP BY marks > 80;

SELECT students WHERE marks > 80;

SELECT * FROM students WHERE marks > 80;

SELECT * FROM students HAVING marks > 80;

None

Which function replaces missing values with a given number?

Deselect Answer

df.replace()

df.fillna()

df.null_replace()

df.dropna()

None

Which of the following is NOT a Power BI component?

Deselect Answer

Power Query

Power Join

Power View

Power Pivot

None

SQL (Top N per Group) You need the top 3 customers by total sales in each region. Which SQL query is correct? 5 Marks

Deselect Answer

SELECT region, customer_id, SUM(amount) AS total_sales FROM Sales s JOIN Customers c ON s.customer_id = c.customer_id GROUP BY region, customer_id ORDER BY region, total_sales DESC LIMIT 3;

SELECT region, customer_id, total_sales FROM ( SELECT c.region, s.customer_id, SUM(s.amount) AS total_sales, ROW_NUMBER() OVER(PARTITION BY c.region ORDER BY SUM(s.amount) DESC) AS rnk FROM Sales s JOIN Customers c ON s.customer_id = c.customer_id GROUP BY c.region, s.customer_id ) t WHERE rnk <= 3;

None of the above

SELECT TOP 3 region, customer_id, SUM(amount) FROM Sales GROUP BY region, customer_id;

None

What is the shape of np.array([[1,2,3],[4,5,6]])?

Deselect Answer

(3,2)

(6,1)

(2,3)

(1,6)

None

Power BI (YTD vs LYTD) You want to calculate Year-to-Date (YTD) sales compared to last year. Which DAX formula is correct? 5 Marks

Deselect Answer

YTD Sales = SUMX(Sales, Sales[Amount])

YTD Sales = TOTALYTD(SUM(Sales[Amount]), Sales[Date]) LYTD Sales = CALCULATE([YTD Sales], SAMEPERIODLASTYEAR(Sales[Date]))

YTD Sales = SUM(Sales[Amount])

YTD Sales = CALCULATE(SUM(Sales[Amount]), DATEADD(Sales[Date], -12, MONTH))

None

Which of the following is not a Python data structure?

Deselect Answer

Set

Stack

List

Dictionary

None

What is the output of list("data")?

Deselect Answer

Error

['d','a','t','a']

['da','ta']

['data']

None

What will df.iloc[0, 1] return?

Deselect Answer

Value at first row, second column

None of the above

Value at first row, first column

Value at second row, first column

None

Which function is used to create pivot tables in Pandas?

Deselect Answer

df.pivot()

df.pivot_table()

Both b and c

pd.pivot_table()

None

Which of the following is used for exception handling in Python?

Deselect Answer

try-except

handle-error

error-resolve

do-catch

None

What does df.describe() do?

Deselect Answer

Describes data types

Drops missing values

Summarizes numeric columns

Shows index info

None

Which SQL clause is used for sorting?

Deselect Answer

HAVING

GROUP BY

SORT BY

ORDER BY

None

Which operation does np.dot(A, B) perform?

Deselect Answer

Summation

Transpose

Matrix multiplication

Element-wise multiplication

None

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