FREE Resources to learn Statistics
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Khan academy: 
https://www.khanacademy.org/math/statistics-probability

Khan academy YouTube: 
https://www.youtube.com/playlist?list=PL1328115D3D8A2566

Statistics by Marin : 
https://www.youtube.com/playlist?list=PLqzoL9-eJTNBZDG8jaNuhap1C9q6VHyVa

Statquest YouTube channel: 
https://www.youtube.com/user/joshstarmer

Free Statistics Books

http://www.sherrytowers.com/cowan_statistical_data_analysis.pdf

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Data Science Jobs

Tata 1mg is hiring Position: Data Scientist Experience: Minimum 1 year Location: Gurgaon Key Responsibilities: Develop and deploy machine learning models to extract insights and drive business decisions. Analyze large datasets to uncover trends, patterns…

? Data science Free Courses

1️⃣ Python for Everybody Course : A great course for beginners to learn Python.

2️⃣ Data analysis with Python course : This course introduces you to data analysis techniques with Python.

3️⃣ Databases & SQL course : You will learn how to manage databases with SQL.

4️⃣ Intro to Inferential Statistics course : This course teaches you how to make predictions by learning statistics.

5️⃣ ML Zoomcamp course : a practical and practical course for learning machine learning.

What ?? ???????? are commonly asked in ???? ??????? ???????????

These are fair game in interviews at ????????, ?????????? & ????? ????.

????????????
- Supervised vs. Unsupervised Learning
- Overfitting and Underfitting
- Cross-validation
- Bias-Variance Tradeoff
- Accuracy vs Interpretability
- Accuracy vs Latency

?? ??????????
- Logistic Regression
- Decision Trees
- Random Forest
- Support Vector Machines
- K-Nearest Neighbors
- Naive Bayes
- Linear Regression
- Ridge and Lasso Regression
- K-Means Clustering
- Hierarchical Clustering
- PCA

???????? ?????
- EDA
- Data Cleaning (e.g. missing value imputation)
- Data Preprocessing (e.g. scaling)
- Feature Engineering (e.g. aggregation)
- Feature Selection (e.g. variable importance)
- Model Training (e.g. gradient descent)
- Model Evaluation (e.g. AUC vs Accuracy)
- Model Productionization

?????????????? ??????
- Grid Search
- Random Search
- Bayesian Optimization

?? ?????
- [Capital One] Detect credit card fraudsters
- [Amazon] Forecast monthly sales
- [Airbnb] Estimate lifetime value of a guest

?✔️Here are Data Analytics-related questions along with their answers:

1.Question: What is the purpose of exploratory data analysis (EDA)?

Answer: EDA is used to analyze and summarize data sets, often through visual methods, to understand patterns, relationships, and potential outliers.

1. Question: What is the difference between supervised and unsupervised learning?

Answer: Supervised learning involves training a model on a labeled dataset, while unsupervised learning deals with unlabeled data to discover patterns without explicit guidance.

3.Question: Explain the concept of normalization in the context of data preprocessing.

Answer: Normalization scales numeric features to a standard range, preventing certain features from dominating due to their larger scales.

1. Question: What is the purpose of a correlation coefficient in statistics?

Answer: A correlation coefficient measures the strength and direction of a linear relationship between two variables, ranging from -1 to 1.

1. Question: What is the role of a decision tree in machine learning?

Answer: A decision tree is a predictive model that maps features to outcomes by recursively splitting data based on feature conditions.

1. Question: Define precision and recall in the context of classification models.

Answer: Precision is the ratio of correctly predicted positive observations to the total predicted positives, while recall is the ratio of correctly predicted positive observations to all actual positives.

1. Question: What is the purpose of cross-validation in machine learning?

Answer: Cross-validation assesses a model's performance by dividing the dataset into multiple subsets, training the model on some, and testing it on others, helping to evaluate its generalization ability.

1. Question: Explain the concept of a data warehouse.

Answer: A data warehouse is a centralized repository that stores, integrates, and manages large volumes of data from different sources, providing a unified view for analysis and reporting.

1. Question: What is the difference between structured and unstructured data?

Answer: Structured data is organized and easily searchable (e.g., databases), while unstructured data lacks a predefined structure (e.g., text documents, images).

1. Question: What is clustering in machine learning?

Answer: Clustering is a technique that groups similar data points together based on certain features, helping to identify patterns or relationships within the data.

Q. Explain the data preprocessing steps in data analysis.Ans. Data preprocessing transforms the data into a format that is more easily and effectively processed in data mining, machine learning and other data science tasks.
1. Data profiling.
2. Data cleansing.
3. Data reduction.
4. Data transformation.
5. Data enrichment.
6. Data validation.

Q. What Are the Three Stages of Building a Model in Machine Learning?Ans. The three stages of building a machine learning model are:

Model Building: Choosing a suitable algorithm for the model and train it according to the requirement

Model Testing: Checking the accuracy of the model through the test data

Applying the Model: Making the required changes after testing and use the final model for real-time projects

Q. What are the subsets of SQL?Ans. The following are the four significant subsets of the SQL:

Data definition language (DDL): It defines the data structure that consists of commands like CREATE, ALTER, DROP, etc.

Data manipulation language (DML): It is used to manipulate existing data in the database. The commands in this category are SELECT, UPDATE, INSERT, etc.

Data control language (DCL): It controls access to the data stored in the database. The commands in this category include GRANT and REVOKE.

Transaction Control Language (TCL): It is used to deal with the transaction operations in the database. The commands in this category are COMMIT, ROLLBACK, SET TRANSACTION, SAVEPOINT, etc.

Q. What is a Parameter in Tableau? Give an Example.Ans. A parameter is a dynamic value that a customer could select, and you can use it to replace constant values in calculations, filters, and reference lines.
For example, when creating a filter to show the top 10 products based on total profit instead of the fixed value, you can update the filter to show the top 10, 20, or 30 products using a parameter.

Top free Data Science resources

@datasciencefun

1. CS109 Data Science
   http://cs109.github.io/2015/pages/videos.html

2. ML Crash Course by Google
   https://developers.google.com/machine-learning/crash-course/

3. Learning From Data from California Institute of Technology
   http://work.caltech.edu/telecourse

4. Mathematics for Machine Learning by University of California, Berkeley
   https://gwthomas.github.io/docs/math4ml.pdf?fbclid=IwAR2UsBgZW9MRgS3nEo8Zh_ukUFnwtFeQS8Ek3OjGxZtDa7UxTYgIs_9pzSI

5. Foundations of Data Science by Avrim Blum, John Hopcroft, and Ravindran Kannan
   https://www.cs.cornell.edu/jeh/book.pdf?fbclid=IwAR19tDrnNh8OxAU1S-tPklL1mqj-51J1EJUHmcHIu2y6yEv5ugrWmySI2WY

6. Python Data Science Handbook
   https://jakevdp.github.io/PythonDataScienceHandbook/?fbclid=IwAR34IRk2_zZ0ht7-8w5rz13N6RP54PqjarQw1PTpbMqKnewcwRy0oJ-Q4aM

7.  CS 221 ― Artificial Intelligence
https://stanford.edu/~shervine/teaching/cs-221/

1. Ten Lectures and Forty-Two Open Problems in the Mathematics of Data Science
   https://ocw.mit.edu/courses/mathematics/18-s096-topics-in-mathematics-of-data-science-fall-2015/lecture-notes/MIT18_S096F15_TenLec.pdf

2. Python for Data Analysis by Boston University
   https://www.bu.edu/tech/files/2017/09/Python-for-Data-Analysis.pptx

10.  Data Mining bu University of Buffalo
https://cedar.buffalo.edu/~srihari/CSE626/index.html?fbclid=IwAR3XZ50uSZAb3u5BP1Qz68x13_xNEH8EdEBQC9tmGEp1BoxLNpZuBCtfMSE

Share the channel link with friends
http://t.me/datasciencefun

Data Science Interview Questions

Question 1 : How would you approach building a recommendation system for personalized content on Facebook? Consider factors like scalability and user privacy.

- Answer: Building a recommendation system for personalized content on Facebook would involve collaborative filtering or content-based methods. Scalability can be achieved using distributed computing, and user privacy can be preserved through techniques like federated learning.

Question 2 : Describe a situation where you had to navigate conflicting opinions within your team. How did you facilitate resolution and maintain team cohesion?

- Answer: In navigating conflicting opinions within a team, I facilitated resolution through open communication, active listening, and finding common ground. Prioritizing team cohesion was key to achieving consensus.

Question 3 : How would you enhance the security of user data on Facebook, considering the evolving landscape of cybersecurity threats?

- Answer: Enhancing the security of user data on Facebook involves implementing robust encryption mechanisms, access controls, and regular security audits. Ensuring compliance with privacy regulations and proactive threat monitoring are essential.

Question 4 : Design a real-time notification system for Facebook, ensuring timely delivery of notifications to users across various platforms.

- Answer: Designing a real-time notification system for Facebook requires technologies like WebSocket for real-time communication and push notifications. Ensuring scalability and reliability through distributed systems is crucial for timely delivery.

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Data Science Interview Questions

1: How would you preprocess and tokenize text data from tweets for sentiment analysis? Discuss potential challenges and solutions.

- Answer: Preprocessing and tokenizing text data for sentiment analysis involves tasks like lowercasing, removing stop words, and stemming or lemmatization. Handling challenges like handling emojis, slang, and noisy text is crucial. Tools like NLTK or spaCy can assist in these tasks.

2: Explain the collaborative filtering approach in building recommendation systems. How might Twitter use this to enhance user experience?

- Answer: Collaborative filtering recommends items based on user preferences and similarities. Techniques include user-based or item-based collaborative filtering and matrix factorization. Twitter could leverage user interactions to recommend tweets, users, or topics.

3: Write a Python or Scala function to count the frequency of hashtags in a given collection of tweets.

- Answer (Python):

def count\_hashtags(tweet\_collection):          hashtags\_count = {}          for tweet in tweet\_collection:              hashtags = [word for word in tweet.split() if word.startswith('\#')]              for hashtag in hashtags:                  hashtags\_count[hashtag] = hashtags\_count.get(hashtag, 0) + 1          return hashtags\_count

4: How does graph analysis contribute to understanding user interactions and content propagation on Twitter? Provide a specific use case.

- Answer: Graph analysis on Twitter involves examining user interactions. For instance, identifying influential users or detecting communities based on retweet or mention networks. Algorithms like PageRank or Louvain Modularity can aid in these analyses.

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