1500+ 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.

The task is to find the total number of ways to make change for a specified value using given denominations.

• Create a dynamic programming table to store the number of ways to make change for each value up to the specified value.

• Iterate through each denomination and update the table accordingly.

• The final answer will be the value in the table at the specified value.

• Consider edge cases such as when the specified value is 0 or when there are no denominations provided.

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

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

The minimum number of comparisons required to identify the heavier coin is 3.

• Divide the 10 coins into 3 groups of 3, 3, and 4 coins.

• Compare the first two groups of 3 coins each. If one group is heavier, move to the next step with that group.

• Compare the 3 coins in the heavier group individually to find the heaviest coin.

Implement inventory management strategies like demand forecasting, safety stock, and efficient logistics.

• Utilize demand forecasting techniques to predict future demand based on historical data and market trends.

• Maintain safety stock levels to buffer against fluctuations in supply and demand.

• Implement efficient logistics and supply chain management to ensure timely delivery of products to stores.

• Utilize technology such as inventory management software to track inventory levels...read more

Choosing an aggregation method for an index depends on the components and their context, ensuring relevance and accuracy.

• Identify the components: Understand what individual metrics or data points will be included in the index.

• Determine the aggregation method: Common methods include sum, average, weighted average, or geometric mean.

• Consider the context: The importance of each component may vary based on the specific application or industry.

• Example: In finance, a stock index mi...read more