# Log **Month of Sep, 2025** * Well sad news, Gitbook has decided to nerf and remove features from its free tier, so there are things which might stop working here pretty soon. The paid tiers are pretty costly for us to afford, but we will keep this website up as long as possible. If you find this helpful, please spread the word and consider donating using the Buy me a coffee button at the top. Given the current job market, we feel this resource might be more relevant than ever. **Month of Feb, 2025** * MLE calculation error updated in the [probability-distribution](https://book.thedatascienceinterviewproject.com/statistics/probability-distribution "mention") page **Month of Oct, 2024** * [Pyspark page](https://book.thedatascienceinterviewproject.com/python/pyspark) added **Month of Sep, 2024** * Pyspark [cheat sheet](https://book.thedatascienceinterviewproject.com/cheat-sheets/pyspark) added **Month of Feb, 2024** * [Clustering](https://book.thedatascienceinterviewproject.com/algorithms/clustering) page updated * Questions added in the [Clustering ](https://book.thedatascienceinterviewproject.com/algorithms/clustering#questions)page
Older Updates **Month of Oct, 2023** * [Problems page](https://book.thedatascienceinterviewproject.com/business-intelligence/power-bi/problems) added in Power BI * [Cheatsheets](https://book.thedatascienceinterviewproject.com/cheat-sheets) pushed to the end of the contents * [Index](https://book.thedatascienceinterviewproject.com/sql/index) added in SQL * [Temp datasets](https://book.thedatascienceinterviewproject.com/sql/temporary-datasets) updated with Table Variable and Temp tables * [Performance Tuning ](https://book.thedatascienceinterviewproject.com/sql/performance-tuning)added in SQL * [Study reference materials](https://book.thedatascienceinterviewproject.com/python/basics) added for Python programming questions * New Problems added in Python and SQL **Month of Sep, 2023** * [Windows Function](https://book.thedatascienceinterviewproject.com/sql/windows-functions) updated. * [A/B test page](https://book.thedatascienceinterviewproject.com/statistics/a-b-test) (WIP) added. * SVR and OLS added in [Regression page](https://book.thedatascienceinterviewproject.com/algorithms/regression). * [Classification metrics](https://book.thedatascienceinterviewproject.com/algorithms/classification#metrics) updated with use cases. * Optimizers and Optimization Criterion updated in [Algorithm overview page](https://book.thedatascienceinterviewproject.com/algorithms). * [Model Building Overview](https://book.thedatascienceinterviewproject.com/model-building/overview) page added. * [Naive Bayes](https://book.thedatascienceinterviewproject.com/algorithms/classification#naive-bayes-algorithm) added in classification. * Many new SQL and Python problems added. * [Confidence Interval](https://book.thedatascienceinterviewproject.com/statistics/central-limit-theorem#what_is_confidence_interval) added in Central Limit Theorem. * Coding [Algorithms from scratch](https://book.thedatascienceinterviewproject.com/python/algorithms-from-scratch) added in Python. * [Common hypothesis tests](https://book.thedatascienceinterviewproject.com/statistics/hypothesis-testing) added. * [Neural Network](https://book.thedatascienceinterviewproject.com/neural-network) section updated **Month of August, 2023** * Vector Database added in the LLM section. * Categorical Encoding added in the data section. * Probability Distribution cheat sheet added. * Algorithm overview page updated. * Bias Variance tradeoff updated. * Linear Regression page updated. * LLM Section updated to Generative AI. * Clustering (WIP) section added. * QUALIFY added in Windows functions page. * We are now on [Instagram](https://www.instagram.com/thedatascienceinterviewbook/) , [TikTok](https://www.tiktok.com/@the.ds.interview?_t=8f1vEGiHYYk&_r=1) and [YouTube](https://youtube.com/@thedatascienceinterviewboo7076), please do follow we will start uploading content soon. * Python in Excel Page added. * Many Python Questions added. * Transformer page added. **Month of May, 2023** * Have enabled GitBook's Lens feature in search, which allow users to ask a question and get answers back from the content of the book itself. This is an experimental feature and supported by OpenAI. Please note this is experimental and can be changed or removed at any moment. * Work on Power BI section started under the Business Intelligence section. * Dark mode and Light mode toggle enabled. **Month of January, 2023** * R Basics cheat sheet added * Python Theoretical Question section updated * Mathematical Motivation Page added **Month of November, 2022** * Group vs Window added * Git added in the new ML Ops section * Platform migration for the book * Cheat Sheet section added * ⚠️ Sign beside pages indicate that work is pending on those * Added questions to Bias/Variance * Python Theoretical section added --> TBA in BOOK **Month of October, 2022** * More questions added to the Time Series Section * Bias/Variance Tradeoff added * Ensemble learning section updated in Decision Tree * MAP vs MLE added in Probability Basics * Basic Overview page added in the Algorithm section **Month of September, 2022** * As per suggestions by users PDF of the book as been made available as a paid extra. It can be purchased from [here](https://www.buymeacoffee.com/dearc/e/88363) * Big O notation section added * Anamoly detection and Time Series section extensively updated * Probability `[FACEBOOK] N Dice`, `[SPOTIFY] MLE of Uniform Distribution`,`Bernoulli trial generator` problem solution updated * Business Scenarios section updated **Month of August, 2022** * Behavioral - Management section added * New interview questions added **Month of July, 2022** * Data sampling section added under data **Month of June, 2022** * We are back post break, keep checking for new content * Machine Learning Framework section added and TensorFlow moved into it * PyCaret added to Machine Learning Framework section **Month of March, 2022** * Hyperparameter optimization section completed * Had an extremely busy last few weeks and the next few months are going to be packed too * Story Telling section added * Quick guide to Visualization added **Month of February, 2022** * Added problems in Python, SQL, Probability * Excel section updated * Data section has been moved into a new and broader section called Model Building * To keep the table of contents clean collapsible headers used in Model Building section * Hyperparameter optimization section added **Month of January, 2022** * Neural Network section added * Added new problems in the Probability section * Added cartoons in a few sections * Outlier section added **Month of December, 2021** * NLP section updated * Got our first bug reported by a reader 😍 **Month of November, 2021** * NLP section updated * Missing values section added * Formatting changes in the Statistics section * Took some break, was obsessively working on this 😌 * New section - Tree based approaches, Industry application added * Decided to make this page a little more interesting * Launched our LinkedIn page do [![Follow LinkedIn](https://img.shields.io/badge/Follow-LinkedIn-0077B5?style=flat-square\&logo=appveyor.svg)](https://www.linkedin.com/company/the-data-science-interview-book/?lipi=urn%3Ali%3Apage%3Ad_flagship3_feed%3BeglbXB3xT0mopZBzReqMEQ%3D%3D), have some interesting plans for it in near future * Added support for dark theme, 🤯 had to remove it as it was breaking a lot of other stuff. Will wait for official support * Added new problems in Probability, Python, Regression, SQL * Added Temporary Datasets and Time page in SQL covering CTEs * Regression section extensively updated **Month of October, 2021** * Major updates to the SQL section * TensorFlow, Excel, Data Sections added * Added new problems in Probability, Python, SQL, Business Case * Cleaned up the formatting issues * Added this change log section * Added Generative VS Discriminative Models section * Completed Hypothesis Testing