Data Science & Machine Learning

20 Must-Know Statistics Questions for Data Analyst and Business Analyst Roles (With Detailed Answers) 1. What is the difference between descriptive and inferential statistics? Descriptive statistics summarize and organize data (e.g., mean, median, mode). Inferential statistics make predictions or inferences about a population based on a sample (e.g., hypothesis testing, confidence intervals). 2. Explain mean, median, and mode and when to use each. Mean is the average; use when data is symmetrically distributed. Median is the middle value; best when data has outliers. Mode is the most frequent value; useful for categorical data. 3. What is standard deviation, and why is it important? It measures data spread around the mean. A low value = less variability; high value = more spread. Important for understanding consistency and risk. 4. Define correlation vs. causation with examples. Correlation: Two variables move together but don't cause each other (e.g., ice cream sales and drowning). Causation: One variable directly affects another (e.g., smoking causes lung cancer). 5. What is a p-value, and how do you interpret it? P-value measures the probability of observing results given that the null hypothesis is true. A small p-value (typically < 0.05) suggests rejecting the null. 6. Explain the concept of confidence intervals. A range of values used to estimate a population parameter. A 95% CI means there's a 95% chance the true value falls within the range. 7. What are outliers, and how can you handle them? Outliers are extreme values differing significantly from others. Handle using: Removal (if due to error) Transformation Capping (e.g., winsorizing) 8. When would you use a t-test vs. a z-test? T-test: Small samples (n < 30) and unknown population standard deviation. Z-test: Large samples and known standard deviation. 9. What is the Central Limit Theorem (CLT), and why is it important? CLT states that the sampling distribution of the sample mean approaches a normal distribution as sample size grows, regardless of population distribution. Essential for inference. 10. Explain the difference between population and sample. Population: Entire group of interest. Sample: Subset used for analysis. Inference is made from the sample to the population. 11. What is regression analysis, and what are its key assumptions? Predicts a dependent variable using one or more independent variables. Assumptions: Linearity, independence, homoscedasticity, no multicollinearity, normality of residuals. 12. How do you calculate probability, and why does it matter in analytics? Probability = (Favorable outcomes) / (Total outcomes). Critical for risk estimation, decision-making, and predictions. 13. Explain the concept of Bayes’ Theorem with a practical example. Bayes’ updates the probability of an event based on new evidence: P(A|B) = [P(B|A) * P(A)] / P(B) Example: Calculating disease probability given a positive test result. 14. What is an ANOVA test, and when should it be used? ANOVA (Analysis of Variance) compares means across 3+ groups to see if at least one differs. Use when comparing more than two groups. 15. Define skewness and kurtosis in a dataset. Skewness: Measure of asymmetry (positive = right-skewed, negative = left). Kurtosis: Measure of tail thickness (high kurtosis = heavy tails, outliers). 16. What is the difference between parametric and non-parametric tests? Parametric: Assumes data follows a distribution (e.g., t-test). Non-parametric: No assumptions; use with skewed or ordinal data (e.g., Mann-Whitney U). 17. What are Type I and Type II errors in hypothesis testing? Type I error: False positive (rejecting a true null). Type II error: False negative (failing to reject a false null). 18. How do you handle missing data in a dataset? Methods: Deletion (listwise or pairwise) Imputation (mean, median, mode, regression) Advanced: KNN, MICE

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SQL Interview Questions with Answers Like for more ❤️

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COMMON TERMINOLOGIES IN PYTHON - PART 1 Have you ever gotten into a discussion with a programmer before? Did you find some of the Terminologies mentioned strange or you didn't fully understand them? In this series, we would be looking at the common Terminologies in python. It is important to know these Terminologies to be able to professionally/properly explain your codes to people and/or to be able to understand what people say in an instant when these codes are mentioned. Below are a few: IDLE (Integrated Development and Learning Environment) - this is an environment that allows you to easily write Python code. IDLE can be used to execute a single statements and create, modify, and execute Python scripts. Python Shell - This is the interactive environment that allows you to type in python code and execute them immediately System Python - This is the version of python that comes with your operating system Prompt - usually represented by the symbol ">>>" and it simply means that python is waiting for you to give it some instructions REPL (Read-Evaluate-Print-Loop) - this refers to the sequence of events in your interactive window in form of a loop (python reads the code inputted>the code is evaluated>output is printed) Argument - this is a value that is passed to a function when called eg print("Hello World")... "Hello World" is the argument that is being passed. Function - this is a code that takes some input, known as arguments, processes that input and produces an output called a return value. E.g print("Hello World")... print is the function Return Value - this is the value that a function returns to the calling script or function when it completes its task (in other words, Output). E.g. >>> print("Hello World") Hello World Where Hello World is your return value. Note: A return value can be any of these variable types: handle, integer, object, or string Script - This is a file where you store your python code in a text file and execute all of the code with a single command Script files - this is a file containing a group of python scripts

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Use of Machine Learning in Data Analytics

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