2000+ Data Analyst Interview Questions and Answers

Code to calculate number of people in a room at EOD given X enter and Y leave throughout the day.

• Create a variable to keep track of the current number of people in the room

• Increment the variable by X every time someone enters the room

• Decrement the variable by Y every time someone leaves the room

• Return the final value of the variable at the end of the day

• Example: If 10 people enter and 5 leave, there will be 5 people in the room at EOD

Distribute chocolates among students to minimize the difference between the largest and smallest number of chocolates.

• Sort the array of chocolates packets in ascending order.

• Iterate through the array and find the minimum difference between the chocolates in packets for each possible distribution to students.

• Return the minimum difference as the result.

Find all unique contiguous substrings of size two from a given string.

• Iterate through the string and extract substrings of size two

• Use a set to store unique substrings

• Return the set as an array of strings

The task is to encode and decode 'SECRET_INFORMATION' for security purposes and determine if the transmission was successful.

• Read the number of test cases 'T'

• For each test case, encode the 'SECRET_INFORMATION' and then decode it

• Compare the decoded string with the original 'SECRET_INFORMATION'

• Print 'Transmission successful' if they match, else print 'Transmission failed'

Calculate the time in minutes required to completely burn a binary tree starting from a given node.

• Traverse the tree to find the start node and calculate the time for fire to spread to all nodes.

• Use a queue to keep track of nodes to be burned next.

• Increment the time for each level of nodes burned.

• Return the total time taken to burn the entire tree.

Find the first repeated character in a given string composed of lowercase English letters.

• Iterate through the string and keep track of characters seen so far in a set.

• Return the first character that is already in the set.

• If no repeated character is found, return '%'.

Find pairs of elements in an array that sum up to a given value, sorted in a specific order.

• Iterate through the array and use a hash set to store elements seen so far.

• For each element, check if the complement (S - current element) is in the set.

• If found, add the pair to the result list and continue.

• Sort the result list based on the criteria mentioned in the problem statement.

Find the equilibrium index of an array where sum of elements on left equals sum on right.

• Iterate through the array and calculate prefix sum and suffix sum at each index.

• Compare prefix sum and suffix sum to find equilibrium index.

• Return the left-most equilibrium index or -1 if none found.

Reverse a given number excluding trailing zeros.

• Iterate through the digits of the number from right to left.

• Skip any trailing zeros while reversing the number.

• Handle the edge case where the number is 0 separately.

• Convert the reversed digits back to a number for the final result.

Transpose a given matrix by switching rows and columns.

• Iterate through the matrix and swap elements at [i][j] with [j][i].

• Create a new matrix to store the transposed values.

• Ensure the dimensions of the transposed matrix are reversed from the original matrix.

Find the third largest element in an array of distinct integers.

• Sort the array in descending order

• Return the element at index 2 as the third largest element

Find the second largest element in an array of integers.

• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.

To find the minimum number from a set of numbers, compare each number with the others and select the smallest.

• Compare each number with the others in the set

• Select the smallest number as the minimum

Explaining a complex joins problem in DBMS

• Discussing the use of different types of joins like inner join, outer join, self join, etc.

• Explaining how to handle null values and duplicates during joins

• Demonstrating a scenario where multiple tables need to be joined based on different keys

Financial statements, cost sheet, debt to equity ratio, stock option, stock split, lease financing, profitability ratios.

• Financial statements are reports that show the financial performance of a company.

• Cost sheet of a bank includes interest expenses and income, while cost sheet of a manufacturing company includes direct and indirect costs.

• Debt to equity ratio is a financial ratio that shows the proportion of debt and equity used to finance a company's assets.

• Stock option is ...read more

Calculate the Nth Fibonacci number efficiently using dynamic programming.

• Use dynamic programming to store and reuse previously calculated Fibonacci numbers.

• Start with base cases F(1) and F(2) as 1, then calculate subsequent Fibonacci numbers.

• Optimize the solution to avoid redundant calculations by storing intermediate results.

• Ensure the implementation handles large values of N efficiently within the given constraints.

To work with dynamic data, remove duplicates and fix errors, use data cleaning techniques.

• Use software tools like OpenRefine or Excel to clean data

• Identify and remove duplicate data using unique identifiers

• Fix errors by standardizing data formats and using regular expressions

• Use data validation to ensure accuracy and completeness

• Create a data cleaning plan and document all changes made

• Test the cleaned data to ensure it meets the desired quality standards

Different approaches for data cleaning include removing duplicates, handling missing values, correcting inconsistent data, and standardizing formats.

• Remove duplicates

• Handle missing values

• Correct inconsistent data

• Standardize formats

• Use statistical methods to identify outliers

• Check for data accuracy and completeness

• Normalize data

• Transform data types

• Apply data validation rules

Questions related to finance and accounting

• IPO stands for Initial Public Offering, which is the first time a company's stock is offered to the public

• Balance sheet has two sides - assets and liabilities & equity

• Depreciation is the decrease in value of an asset over time due to wear and tear or obsolescence

• Financial statements include income statement, balance sheet, and cash flow statement

The amount of petrol used in a city in one day varies depending on factors like population, transportation infrastructure, and fuel prices.

• Petrol usage depends on the number of vehicles in the city.

• Public transportation options can impact petrol consumption.

• Economic factors such as fuel prices and income levels play a role in petrol usage.

• Industrial activities and power generation also contribute to petrol consumption.

• Environmental policies and initiatives can influence petro...read more

The sequence of execution of SQL codes is Select-From-Where-Group By-Having-Order By.

• Select: choose the columns to display

• From: specify the table(s) to retrieve data from

• Where: filter the data based on conditions

• Group By: group the data based on a column

• Having: filter the grouped data based on conditions

• Order By: sort the data based on a column

A machine breakdown led to production delays, prompting the implementation of improved maintenance protocols and monitoring systems.

• Identified the root cause: unexpected machine breakdown due to lack of preventive maintenance.

• Implemented a preventive maintenance schedule, reducing future breakdowns by 30%.

• Introduced real-time monitoring systems to track machine performance and predict failures.

• Conducted training sessions for staff on the importance of maintenance and monitori...read more

The number of pizzas sold in Pune in one day varies depending on factors like day of the week, weather, events, etc.

• The number of pizzas sold in Pune can range from hundreds to thousands in a day.

• Factors like day of the week (weekend vs weekday), weather (rainy vs sunny), events (festivals, holidays) can impact the sales.

• Popular pizza outlets in Pune like Domino's, Pizza Hut, etc. contribute to the overall sales.

• Data from previous sales records, market research, and customer ...read more

The financial statements (BS, IS, CF) have common elements such as assets, liabilities, equity, revenue, expenses, and cash flows.

• Assets: resources owned by the company

• Liabilities: obligations owed by the company

• Equity: residual interest in the assets of the company

• Revenue: income generated by the company

• Expenses: costs incurred by the company

• Cash flows: inflows and outflows of cash

Questions related to data analysis techniques and methods.

• Bais and variance trade-off: balancing model complexity and accuracy

• Handling imbalanced data: resampling techniques, adjusting class weights, using different evaluation metrics

• Multicollinearity: when predictor variables are highly correlated, can be handled by feature selection or regularization

• Lasso & Ridge: regularization techniques to prevent overfitting by adding penalty terms to the loss function

• Bagging vs Boostin...read more