Essential NumPy Functions for Data Analysis

Array Creation:

np.array() - Create an array from a list.

np.zeros((rows, cols)) - Create an array filled with zeros.

np.ones((rows, cols)) - Create an array filled with ones.

np.arange(start, stop, step) - Create an array with a range of values.


Array Operations:

np.sum(array) - Calculate the sum of array elements.

np.mean(array) - Compute the mean.

np.median(array) - Calculate the median.

np.std(array) - Compute the standard deviation.


Indexing and Slicing:

array[start:stop] - Slice an array.

array[row, col] - Access a specific element.

array[:, col] - Select all rows for a column.


Reshaping and Transposing:

array.reshape(new_shape) - Reshape an array.

array.T - Transpose an array.


Random Sampling:

np.random.rand(rows, cols) - Generate random numbers in [0, 1).

np.random.randint(low, high, size) - Generate random integers.


Mathematical Operations:

np.dot(A, B) - Compute the dot product.

np.linalg.inv(A) - Compute the inverse of a matrix.

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Data Analyst Learning Plan in 2025

|-- Week 1: Introduction to Data Analytics
| |-- What is Data Analytics?
| |-- Roles & Responsibilities of a Data Analyst
| |-- Data Analytics Workflow
| |-- Types of Data (Structured, Unstructured, Semi-structured)
|
|-- Week 2: Excel for Data Analysis
| |-- Excel Basics & Interface
| |-- Data Cleaning & Preparation
| |-- Formulas, Functions, Pivot Tables
| |-- Dashboards & Reporting in Excel
|
|-- Week 3: SQL for Data Analysts
| |-- SQL Basics: SELECT, WHERE, ORDER BY
| |-- Aggregations & GROUP BY
| |-- Joins: INNER, LEFT, RIGHT, FULL
| |-- CTEs, Subqueries & Window Functions
|
|-- Week 4: Python for Data Analysis
| |-- Python Basics (Variables, Data Types, Loops)
| |-- Data Analysis with Pandas
| |-- Data Visualization with Matplotlib & Seaborn
| |-- Exploratory Data Analysis (EDA)
|
|-- Week 5: Statistics & Probability
| |-- Descriptive Statistics
| |-- Probability Theory Basics
| |-- Distributions (Normal, Binomial, Poisson)
| |-- Hypothesis Testing & A/B Testing
|
|-- Week 6: Data Cleaning & Transformation
| |-- Handling Missing Values
| |-- Duplicates, Outliers, and Data Formatting
| |-- Data Parsing & Regex
| |-- Data Normalization
|
|-- Week 7: Data Visualization Tools
| |-- Power BI Basics
| |-- Creating Reports and Dashboards
| |-- Data Modeling in Power BI
| |-- Filters, Slicers, DAX Basics
|
|-- Week 8: Advanced Excel & Power BI
| |-- Advanced Charts & Dashboards
| |-- Time Intelligence in Power BI
| |-- Calculated Columns & Measures (DAX)
| |-- Performance Optimization Tips
|
|-- Week 9: Business Acumen & Domain Knowledge
| |-- KPIs & Business Metrics
| |-- Understanding Financial, Marketing, Sales Data
| |-- Creating Insightful Reports
| |-- Storytelling with Data
|
|-- Week 10: Real-World Projects & Portfolio
| |-- End-to-End Project on E-commerce/Sales
| |-- Collecting & Cleaning Data
| |-- Analyzing Trends & Presenting Insights
| |-- Uploading Projects on GitHub
|
|-- Week 11: Tools for Data Analysts
| |-- Jupyter Notebooks
| |-- Google Sheets & Google Data Studio
| |-- Tableau Overview
| |-- APIs & Web Scraping (Intro only)
|
|-- Week 12: Career Preparation
| |-- Resume & LinkedIn for Data Analysts
| |-- Common Interview Questions (SQL, Python, Case Studies)
| |-- Mock Interviews & Peer Reviews

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📚👀🚀Preparing for a Data science/ Data Analytics interview can be challenging, but with the right strategy, you can enhance your chances of success. Here are some key tips to assist you in getting ready:

Review Fundamental Concepts: Ensure you have a strong grasp of statistics, probability, linear algebra, data structures, algorithms, and programming languages like Python, R, and SQL.

Refresh Machine Learning Knowledge: Familiarize yourself with various machine learning algorithms, including supervised, unsupervised, and reinforcement learning.

Practice Coding: Sharpen your coding skills by solving data science-related problems on platforms like HackerRank, LeetCode, and Kaggle.

Build a Project Portfolio: Showcase your proficiency by creating a portfolio highlighting projects covering data cleaning, wrangling, exploratory data analysis, and machine learning.

Hone Communication Skills: Practice articulating complex technical ideas in simple terms, as effective communication is vital for data scientists when interacting with non-technical stakeholders.

Research the Company: Gain insights into the company's operations, industry, and how they leverage data to solve challenges.

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•Install and Explore Power BI: Familiarize yourself with the interface.
•Import Data: Learn to import and transform data using Power BI.

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•Relationships: Understand and establish relationships between tables.
•DAX (Data Analysis Expressions): Learn the basics of DAX for calculations.

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•Custom Measures and Columns: Utilize DAX for customized data calculations.

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1️⃣ What is the difference between supervised and unsupervised learning?
Supervised learning involves learning from labeled data to predict outcomes while unsupervised learning involves finding patterns in unlabeled data.

2️⃣ Explain the bias-variance tradeoff in machine learning.
The bias-variance tradeoff is a key concept in machine learning. Models with high bias have low complexity and over-simplify, while models with high variance are more complex and over-fit to the training data. The goal is to find the right balance between bias and variance.

3️⃣ What is the Central Limit Theorem and why is it important in statistics?
The Central Limit Theorem (CLT) states that the sampling distribution of the sample means will be approximately normally distributed regardless of the underlying population distribution, as long as the sample size is sufficiently large. It is important because it justifies the use of statistics, such as hypothesis testing and confidence intervals, on small sample sizes.

4️⃣ Describe the process of feature selection and why it is important in machine learning.
Feature selection is the process of selecting the most relevant features (variables) from a dataset. This is important because unnecessary features can lead to over-fitting, slower training times, and reduced accuracy.

5️⃣ What is the difference between overfitting and underfitting in machine learning? How do you address them?
Overfitting occurs when a model is too complex and fits the training data too well, resulting in poor performance on unseen data. Underfitting occurs when a model is too simple and cannot fit the training data well enough, resulting in poor performance on both training and unseen data. Techniques to address overfitting include regularization and early stopping, while techniques to address underfitting include using more complex models or increasing the amount of input data.

6️⃣ What is regularization and why is it used in machine learning?
Regularization is a technique used to prevent overfitting in machine learning. It involves adding a penalty term to the loss function to limit the complexity of the model, effectively reducing the impact of certain features.

7️⃣ How do you handle missing data in a dataset?
Handling missing data can be done by either deleting the missing samples, imputing the missing values, or using models that can handle missing data directly.

8️⃣ What is the difference between classification and regression in machine learning?
Classification is a type of supervised learning where the goal is to predict a categorical or discrete outcome, while regression is a type of supervised learning where the goal is to predict a continuous or numerical outcome.

9️⃣ Explain the concept of cross-validation and why it is used.
Cross-validation is a technique used to evaluate the performance of a machine learning model. It involves spliting the data into training and validation sets, and then training and evaluating the model on multiple such splits. Cross-validation gives a better idea of the model's generalization ability and helps prevent over-fitting.

🔟 What evaluation metrics would you use to evaluate a binary classification model?
Some commonly used evaluation metrics for binary classification models are accuracy, precision, recall, F1 score, and ROC-AUC. The choice of metric depends on the specific requirements of the problem.

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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.