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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

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

Deselect Answer

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

['data']

['da','ta']

Error

None

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

Deselect Answer

Discrete

Ordinal

Categorical

Continuous

None

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

Deselect Answer

Error

[3,2,1]

[1,2,3]

None

None

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

Deselect Answer

Plotly

Seaborn

Matplotlib

ggplot2

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 SQL inside Pandas with pd.read_sql()

Loop through each column with for and apply fillna()

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

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

None

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

Deselect Answer

Error

None

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

Deselect Answer

np.zeros()

np.array(0)

np.ones()

np.empty()

None

Which keyword is used to define a function in Python?

Deselect Answer

fun

def

function

define

None

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

Deselect Answer

pd.csv_read()

pd.load_csv()

pd.read()

pd.read_csv()

None

Which function is used to create pivot tables in Pandas?

Deselect Answer

Both b and c

df.pivot()

pd.pivot_table()

df.pivot_table()

None

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

Deselect Answer

(6,1)

(3,2)

(1,6)

(2,3)

None

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

Deselect Answer

do-catch

try-except

handle-error

error-resolve

None

What is the output of bool([])?

Deselect Answer

Error

False

True

None

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

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

YTD Sales = SUM(Sales[Amount])

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

None

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

Deselect Answer

Unique values in column

Count of unique values

None

Index of unique rows

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

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])

Use nested for loops

arr[arr < 0] = 0

None

Which Pandas function is used to combine DataFrames vertically?

Deselect Answer

pd.merge()

pd.append()

pd.concat()

pd.join()

None

Which method gives the first 5 rows of a DataFrame?

Deselect Answer

df.first()

df.top()

df.head()

df.tail()

None

What does df.describe() do?

Deselect Answer

Summarizes numeric columns

Describes data types

Drops missing values

Shows index info

None

Which method writes a DataFrame to Excel?

Deselect Answer

df.to_excel()

df.to_csv()

df.save_excel()

df.write_excel()

None

What does len("Data Science") return?

Deselect Answer

13

11

12

10

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)

Use list.count() in a loop

Sort the list and take first 3 values

Convert to Pandas DataFrame and use value_counts()

None

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

Deselect Answer

Summation

Transpose

Matrix multiplication

Element-wise multiplication

None

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

Deselect Answer

DISTINCT

HAVING

UNIQUE

GROUP BY

None

Which of the following is NOT a Power BI component?

Deselect Answer

Power View

Power Pivot

Power Join

Power Query

None

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

Deselect Answer

dropna()

None of the above

fillna()

Both a and b

None

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

Deselect Answer

tuple

array

range object

list

None

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

Deselect Answer

Right Join

Left Join

Inner Join

Full Join

None

Which method sorts values in Pandas DataFrame?

Deselect Answer

None

df.sort_index()

Both a and b

df.sort_values()

None

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

Deselect Answer

df.dimension

df.size

df.shape

df.length

None

Which function replaces missing values with a given number?

Deselect Answer

df.dropna()

df.null_replace()

df.fillna()

df.replace()

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, 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;

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;

None of the above

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

None

Which SQL clause is used for sorting?

Deselect Answer

GROUP BY

ORDER BY

SORT BY

HAVING

None

Which function is used to merge two DataFrames?

Deselect Answer

pd.concat()

pd.merge()

pd.join()

All of the above

None

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

Deselect Answer

SELECT * FROM students HAVING marks > 80;

SELECT students WHERE marks > 80;

SELECT * FROM students WHERE marks > 80;

SELECT * FROM students GROUP BY marks > 80;

None

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

Deselect Answer

6

2

3

1

None

Which language is used in Power BI for data modeling?

Deselect Answer

SQL

DAX

R

Python

None

Which of the following is not a Python data structure?

Deselect Answer

Dictionary

Set

List

Stack

None

Which module in Python is used for regular expressions?

Deselect Answer

regex

re

pattern

string

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

Deselect Answer

Data Degradation

Model Training

Data Cleaning

Data Collection

None

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

Deselect Answer

Matrix

TreeMap

Bar chart

Heatmap

None

Which of the following is mutable in Python?

Deselect Answer

Integer

List

String

Tuple

None

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

Deselect Answer

None of the above

Value at first row, second column

Value at second row, first column

Value at first row, first column

None

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

Deselect Answer

GROUP BY

HAVING

WHERE

ORDER BY

None

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