Data Analysis Process Quiz
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Questions and Answers

Which of the following is the primary focus of the initial 'Problem Understanding' phase in the data analysis process?

  • Understanding project goals from a business viewpoint and converting them into a data analysis problem. (correct)
  • Constructing the final dataset by joining different data sources.
  • Developing statistical models to analyze data patterns.
  • Identifying data quality problems and anomalies.
  • During the 'Data Understanding' phase, what is one of the core questions you should aim to answer?

  • Who collected the data and using what method? (correct)
  • How should we normalize our data?
  • How can we deploy our findings?
  • What statistical models should be used?
  • Which of these actions is primarily performed during the 'Data Preparation' phase?

  • Identifying business needs and objectives.
  • Reducing the number of variables to only those relevant for the process. (correct)
  • Selecting the correct model for data analysis.
  • Developing a preliminary plan to achieve specific aims.
  • What does the data preparation phase not primarily involve?

    <p>Defining the project's business objectives. (B)</p> Signup and view all the answers

    Which of these is a key purpose of the 'Data Understanding' phase?

    <p>To get familiar with the data and evaluate its quality. (A)</p> Signup and view all the answers

    If a data analysis project has an unclear business problem, which phase would likely need to be revisited or given more focus to provide clarity?

    <p>Problem Understanding (D)</p> Signup and view all the answers

    What activity from the list below is more likely to be done in data preparation phase rather than in data understanding?

    <p>Normalizing the data. (C)</p> Signup and view all the answers

    Which of these is the typical order of phases in a data analysis process?

    <p>Problem Understanding -&gt; Data Understanding -&gt; Data Preparation -&gt; Modeling. (C)</p> Signup and view all the answers

    What impact do outliers have on machine learning models?

    <p>Longer model training times, decreased accuracy, increased error variance, and decreased normality. (A)</p> Signup and view all the answers

    Which of the following methods is NOT used to detect outliers?

    <p>Min-Max Normalization (D)</p> Signup and view all the answers

    What is the primary purpose of feature scaling?

    <p>To enhance the efficiency of the machine learning process. (A)</p> Signup and view all the answers

    What is the primary focus of the data analysis process during the 'Modeling' phase?

    <p>Selecting and applying various modeling techniques and calibrating their parameters. (B)</p> Signup and view all the answers

    What is the mean and standard deviation of normalized values after applying the z-score standardization?

    <p>Mean of 0 and standard deviation of 1. (A)</p> Signup and view all the answers

    In min-max normalization, what is the typical range that the original data is transformed into?

    <p>[0, 1] (C)</p> Signup and view all the answers

    Which of these activities is a key component of the 'Evaluation' phase in data analysis?

    <p>Determining if the model meets assumptions and if all objectives were accounted for. (C)</p> Signup and view all the answers

    What is the primary goal of the 'Deployment' phase in data analysis?

    <p>Organizing the knowledge obtained and presenting it for the customer. (C)</p> Signup and view all the answers

    A machine learning model has an AUC score of 0.65. How would this model be classified?

    <p>Poor classifier (C)</p> Signup and view all the answers

    What does the term 'Machine learning models' refer to?

    <p>Algorithms that can find patterns or create predictions from not yet seen data. (A)</p> Signup and view all the answers

    Why is Python a popular language for machine learning?

    <p>It is known for its readability, simplicity, and rich libraries for machine learning. (C)</p> Signup and view all the answers

    Which of the following best describes the role of libraries like Scikit-learn, TensorFlow, and Pandas in Python for machine learning?

    <p>They provide prebuilt functions which help to reduce the amount of code you have to write. (C)</p> Signup and view all the answers

    What is the formula for calculating the False Positive Rate (FPR)? given TP (True Positives), TN (True Negatives), FP (False Positives), FN (False Negatives)

    <p>FP / (TN + FP) (C)</p> Signup and view all the answers

    In the context of the data analysis process, which phase directly precedes the 'Deployment' phase?

    <p>Evaluation (A)</p> Signup and view all the answers

    What is the primary reason given in the content for why the creation of a model is generally not the end of a project?

    <p>The knowledge gained needs to be presented so the customer can use it. (C)</p> Signup and view all the answers

    Besides readability, what specific advantage does the content mention regarding Python's use in machine learning?

    <p>Python has prebuilt mathematical and machine learning functions in different libraries. (A)</p> Signup and view all the answers

    According to the CRISP-DM methodology, which phase directly follows 'Data Understanding'?

    <p>Data Preparation (A)</p> Signup and view all the answers

    In the context of machine learning, what is the primary reason for preprocessing a dataset before applying an algorithm?

    <p>To improve the algorithm's learning by ensuring data quality and information content. (D)</p> Signup and view all the answers

    What is the singular form of 'data'?

    <p>datum (A)</p> Signup and view all the answers

    In Euclid's work 'Dedomena', what is the term 'data' considered to be?

    <p>A quantity resulting directly from the terms of a given problem. (B)</p> Signup and view all the answers

    If a dataset is represented as a matrix of type m x n, what does m represent?

    <p>The number of observations (records). (B)</p> Signup and view all the answers

    In record-based data, what is another term for output variables?

    <p>Target variables. (A)</p> Signup and view all the answers

    Which of the following best describes how a record is structured in a typical dataset?

    <p>A set of attributes with a fixed tuple length. (C)</p> Signup and view all the answers

    What is a fundamental characteristic of input variables in the context of machine learning?

    <p>They are also known as descriptive variables. (A)</p> Signup and view all the answers

    What is the primary purpose of using descriptive statistics in data analysis?

    <p>To understand the data, quantify results, and measure application performance. (A)</p> Signup and view all the answers

    What does a distribution in a dataset represent?

    <p>The frequency of each unique value in a dataset. (D)</p> Signup and view all the answers

    Which of the following is NOT considered a central tendency measure?

    <p>Standard Deviation. (D)</p> Signup and view all the answers

    How is the mean calculated for a given dataset?

    <p>By summing all the values and dividing by the total count of values. (B)</p> Signup and view all the answers

    What does the median represent in a sorted dataset?

    <p>The value separating the lower and upper halves of the dataset. (B)</p> Signup and view all the answers

    What is the primary focus of spread or dispersion measures in statistics?

    <p>To measure the variability or scattering of values across a dataset. (A)</p> Signup and view all the answers

    Which measure of central tendency is most affected by outliers in a dataset?

    <p>The mean. (B)</p> Signup and view all the answers

    What is the most appropriate way to describe a sample of data using the measures described in the document?

    <p>By reporting mean, median and a measure of spread for a balanced view of the data. (C)</p> Signup and view all the answers

    How are anomalies typically detected, according to the text?

    <p>Based on the likelihood of the data under the Gaussian distribution. (B)</p> Signup and view all the answers

    What is the primary function of Principal Component Analysis (PCA) in the context of dimensionality reduction?

    <p>To identify directions of maximum variance in the data. (B)</p> Signup and view all the answers

    Which kernel is most commonly used in kernelized machine learning techniques?

    <p>Gaussian kernel (A)</p> Signup and view all the answers

    What does the central limit theorem indicate about the sampling distribution as the sample size increases?

    <p>It approaches a normal distribution. (D)</p> Signup and view all the answers

    According to the central limit theorem, what happens to the mean of the sample as sample size increases?

    <p>It gets closer to the population mean. (C)</p> Signup and view all the answers

    What is the role of sampling in the data analysis process?

    <p>To infer information about the population using a smaller subset. (D)</p> Signup and view all the answers

    What is the initial move in the data analysis system toward easily understanding and communicating information?

    <p>Data Visualization. (A)</p> Signup and view all the answers

    What happens to the standard deviation of the sample as sample size increases, according to the central limit theorem?

    <p>It reduces. (D)</p> Signup and view all the answers

    Flashcards

    Problem Understanding

    The first step in the data analysis process, where you clearly define the project goals and translate them into a data-driven problem statement.

    Data Understanding

    This phase involves gaining a deep understanding of the data, answering crucial questions about its origin, collection methods, and meaning.

    Data Preparation

    Involves preparing your raw data for analysis by cleaning, transforming, and combining datasets to build a cohesive and usable dataset.

    Modeling

    This stage applies statistical and machine learning techniques to analyze the curated data and build models that meet the defined objectives.

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    Evaluation

    This stage involves evaluating the performance of the developed models to assess their accuracy, reliability, and potential effectiveness in solving the problem.

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    Deployment

    This final step involves putting the best performing model into practice, integrating it into systems or processes to achieve the desired outcome.

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    Modeling in Data Analysis

    In this stage, different modeling techniques are selected, configured, and optimized.

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    Evaluating Models in Data Analysis

    This phase focuses on evaluating if the created model meets the initial goals and objectives. It also checks for any missing aspects or business needs.

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    Deploying Models in Data Analysis

    Even if the model's purpose is to learn from data, the knowledge gained needs to be organized and presented in a way that makes sense to the user.

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    Why is Python preferred for machine learning?

    Python is known for its clear and simple code, making it easy to learn for beginners and efficient for experts.

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    What libraries support machine learning in Python?

    Python offers various libraries and frameworks (like Scikit-learn, TensorFlow, PyTorch, Keras, and Pandas) that offer ready-made tools for data analysis and machine learning tasks.

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    What are the benefits of Python libraries for machine learning?

    These libraries in Python offer built-in functions and utilities for math operations, data manipulation, and machine learning, reducing the need to write code from scratch.

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    What is data analysis?

    The process of data analysis involves collecting, cleaning, transforming, and analyzing data to extract meaningful insights and support decision-making.

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    Why is data analysis important?

    Data analysis aims to gain insights and knowledge from data to solve problems, improve processes, and make informed decisions.

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    Mean

    The central tendency measure that represents the average of a dataset calculated by summing all values and dividing by the total count.

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    Median

    The central tendency measure that represents the middle value in a sorted dataset, separating the lower half from the upper half.

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    Spread or Dispersion Measures

    Measures that indicate the spread or variability of data points within a dataset.

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    Distribution

    A visual representation of how frequently values appear within a dataset. It shows the distribution of data points.

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    Descriptive Statistics

    A field in statistics that helps us understand and quantify data, and is essential for evaluating the performance of machine learning models.

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    Central Tendency Measures

    A type of statistical measure that helps determine the central location of data points within a distribution.

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    Data Cleaning

    The practice of preparing data for analysis by addressing issues such as inconsistencies, missing values, and data format discrepancies.

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    What is data in the context of machine learning?

    In machine learning, data is often represented as a collection of records. Each record represents a single observation or sample, described by a set of attributes or variables.

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    What is a record in machine learning?

    In machine learning, each record, also known as an observation or sample, is described by a specific set of attributes or variables. Each record represents a unique instance within the dataset.

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    What are attributes in machine learning?

    In machine learning, attributes are the characteristics or variables that describe each record in the dataset. They represent the features or properties of the data.

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    What are input variables in machine learning?

    Input variables, also known as independent variables, are the features used to predict the target variable. They are the factors that influence the outcome.

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    What are output variables in machine learning?

    Output variables, also known as dependent variables, are the target or label you are trying to predict. They are the outcomes you want to understand.

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    What are transaction-based sets in machine learning?

    Transaction-based datasets often involve a series of events or actions, and each transaction is represented as a vector. The vectors usually describe properties of each transaction.

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    What is CRISP-DM and its purpose?

    The CRISP-DM (Cross Industry Process for Data Mining) is a structured framework for conducting data mining projects. It outlines a six-phase process for effective data analysis.

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    Why is data preprocessing important for machine learning?

    The quality and information content of a dataset are crucial for machine learning algorithms to learn effectively. Preprocessing data before using it in machine learning is vital.

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    Anomaly Detection

    Anomalies are identified by examining how likely the data is to occur under a normal distribution.

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    Principal Component Analysis (PCA)

    A method used to reduce the number of dimensions in a dataset by transforming it into a smaller set of variables called principal components. This helps to find the directions of maximum variance in the data.

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    Kernel Methods

    A technique used in machine learning algorithms where data is mapped into a higher-dimensional space using a kernel function. This is often used to improve the accuracy of models.

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    Central Limit Theorem

    The central limit theorem states that the distribution of sample means will approach a normal distribution as the sample size increases. This is a fundamental principle for hypothesis testing.

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    Sample (in Data Analysis)

    It's a subset of data that represents the characteristics of the entire population. It's used for analysis when collecting data for the whole population is impossible.

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    Sampling

    The process of collecting data for research or analysis.

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    Data Visualization

    The process of creating visualizations to present data in a clear and understandable way.

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    Normal Distribution Assumption

    Statistical tests and confidence intervals rely on the assumption that the population data follows a normal distribution.

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    What are outliers?

    Outliers are data points that are significantly different from the rest of the data. They can cause problems when it comes to building predictive models.

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    How do outliers impact predictive models?

    Outliers can affect the accuracy and efficiency of predictive models. This can lead to longer training times, inaccurate predictions, and higher error variance.

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    What is a Box Plot?

    A box plot is a visual representation of data that shows the distribution of the data and identifies outliers. It uses quartiles to divide the data into groups, with the outliers displayed as individual points.

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    What is a Z-score?

    The Z-score is a statistical measure that indicates how many standard deviations a data point is from the mean. Outliers often have a high Z-score, indicating they are far from the mean.

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    What is data transformation?

    Data transformation involves changing the structure or characteristics of your data to improve its suitability for analysis. This can include scaling data or using techniques like standardization.

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    What is Z-score standardization?

    Z-score standardization transforms data to have a mean of 0 and a standard deviation of 1. This makes features comparable and can improve model performance.

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    What is Min-Max normalization?

    Min-Max normalization changes data values to a range between 0 and 1. This is another way to scale features and make them comparable.

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    What is AUC in Machine Learning?

    AUC (Area Under the Curve) measures the overall performance of a classification model. An AUC of 0.5 means no discrimination; a score of 0.7 and above suggests good performance.

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    Study Notes

    Machine Learning

    • Machine learning (ML) is a computer science field studying algorithms and techniques for automating solutions to complex problems.
    • Coined around 1960, it combines "machine" (computer, robot, etc.) and "learning" (acquiring or discovering patterns).

    Bibliography

    • Provides a list of various books and resources on data mining and machine learning.

    • Includes URLs for additional sources.

    Big Data

    • The University of Lodz Library holds approximately 2.8 million volumes.
    • Assuming an average document size of 1MB, the library's equivalent digital storage would be 30 terabytes.
    • A courier company's shipment database is roughly 20 terabytes.
    • The documents list various unit prefixes for data storage (KB, MB, GB, TB, PB, EB, ZB, YB, YIB).

    Machine Learning Definition

    • Data mining is the art and science of intelligent data analysis aiming to uncover meaningful insights and knowledge from data.
    • This often involves creating models that capture the essence of discovered knowledge, enabling better understanding and prediction.

    Data Mining vs Machine Learning

    • Data mining focuses on discovering patterns in data that are precise, new, useful, and understandable.
    • Machine learning uses algorithms to automatically improve through data-based experience, constructing models to predict future results. This often employs data mining techniques.

    What is not Data Mining and Machine Learning

    • Data mining and Machine learning are distinct from OLAP (online analytical processing).
    • OLAP focuses on querying and summarizing data, not on extracting patterns or making predictions.

    Data Analysis Process

    • The Cross-Industry Standard Process for Data Mining (CRISP-DM) is a widely used framework for data analysis projects.

    • CRISP-DM includes six phases:

    • Problem understanding (Business understanding)

    • Data understanding

    • Data preparation

    • Modeling

    • Evaluation

    • Deployment

    • These phases are iterative and often overlap.

    Data Analysis Process - Specific steps

    • Problem Understanding/Business Understanding: Understanding the business aims and requirements
    • Data Understanding: Becoming familiar with the data, identifying data quality issues
    • Data Preparation: Constructing the final dataset from raw data (e.g., joining multiple data sets, cleaning, and reducing variables)
    • Modeling: Selecting and applying modeling techniques, calibrating parameters
    • Evaluation: Determining whether the model fits assumptions, evaluating performance against business objectives
    • Deployment: Implementing and presenting the model's insights in a user-friendly format

    Data Quality

    • Machine learning algorithms are sensitive to data quality, meaning flawed data leads to erroneous results.
    • "Garbage in, garbage out" (GIGO) is a principle emphasizing data quality's importance.
    • Data quality has three fundamental properties: completeness, correctness, and actuality.

    Types of Variable

    • Data type influences data analysis and visualization.
    • Qualitative (categorical): Non-numerical data (names, labels).
    • Nominal: Unordered categories (e.g., colors, names of products)
    • Ordinal: Ordered categories (e.g., ratings, education levels)
    • Quantitative (numerical): Measured using integer or real values
    • Discrete: Finite countable values (e.g., number of items).
    • Continuous: Uncountable values (e.g., height, weight)

    Qualitative data - types

    • Nominal attributes - labels or names that represent different categories

    • Ordinal attributes - have a meaningful order or ranking.

    Quantitative data - types

    • Discrete attributes - those are finite countable set of values.

    • Continuous attributes - have uncountable values, such as height or weight.

    Single-valued variables

    • Single-valued variables do not contain information and therefore are not used in data analysis.
    • Such variables should be checked in data for analysis to ensure the model performance is not impacted.

    Types of Data - Transaction-based sets

    • Data organized as transactions for the business analysis of items purchased by customers.
    • Each transaction is represented by a vector of items.

    Data in graph form

    • Data visualizations often depict relationships using graphs with vertices storing data and edges for relationships.

    Data Quality - More Information

    • Data quality is critical in building machine learning models as inaccuracies can result in poor performance.

    Noise in Data

    • Label noise: Incorrect labeling of observations.

    • Inconsistent observations: Erroneous or inconsistent data.

    • Classification errors: Observations labeled as a class they don't belong to.

    • Data noise is synonymous with corrupted data for analysis purpose.

    • Attribute noise: Incorrect or missing attribute values.

    Data Analysis Engineering

    • Data science depends on several factors like programming, machine learning, statistics, data engineering, and visualization.

    Python and Machine Learning

    • Python is a popular choice for machine learning due to its readability, intuitive syntax, and extensive libraries (e.g., Scikit-learn, TensorFlow, PyTorch).

    Python 4 ML - Libraries

    • NumPy is a fundamental library for scientific computing, providing support for arrays and matrices.
    • Pandas is essential for data manipulation and analysis, providing data structures for numerical tables and time series.
    • Matplotlib is excellent for creating static, interactive, and animated visualizations in Python.
    • Scikit-learn provides supervised and unsupervised learning algorithms, along with relevant tools for model selection and evaluation.
    • SciPy extends capabilities of NumPy with optimization, regression, interpolation, eigenvector decomposition.

    Data Analysis Process - Flow

    • Dataset: Raw and Matrix data.
    • Training Set Training data for model building
    • Test Set: Assessing model performance on unseen data to test accuracy and generalize well.

    Data Pre-processing

    • Data preprocessing is crucial (typically 70-80% of the knowledge discovery process).
    • Includes: data cleaning (fixing errors, removing duplicates, etc.), restructuring data to match required format, merging datasets, etc.

    Data Types (summary)

    • Data classification can be by attributes (Categorical, numerical, ordered data, etc.)

    Data Visualization (general)

    • Visualizing data is valuable in understanding trends, outliers, distributions, relationships, etc.
    • Uses visual elements such as charts, graphs, plots, and maps.

    Data Visualization - Comparisons

    • Comparison visualizations illustrate differences over time.
    • Box plots effectively compare distributions of continuous variables across categories.

    Visualizing numeric features - Box plots

    • Displays five-number summary (minimum, 1st quartile, median, 3rd quartile, maximum) and outliers individually.

    Data Visualization

    • Scatterplots show relationships between two or more continuous variables.

    • Histograms visually represent the distribution of numerical data values by showing how frequently values appear.

    • Heatmaps are intelligent analytical tools using a color system to show various different values.

    • Pair plots show relationships among pairs of variables in numerical datasets providing distributions and correlations.

    Knowledge and Information

    • Data provides raw, descriptive facts and figures; information is a result of interpreting or processing data; knowledge often arises from observing or reasoning across multiple data points, potentially revealing deeper insights or patterns not directly apparent from individual data points.

    Data Analysis

    • Data analysis (e.g. via CRISP-DM methodology) involves understanding issues, data examination and preparation, selection/fitting/training and evaluation of a model for a particular issue.

    Normal Distribution

    • A symmetrical, bell-shaped continuous probability distribution, used in many machine learning algorithms and statistical methods.
    • The mean, median, and mode are at the peak.
    • Measures of spread are commonly related to standard deviation; 68% data in one standard deviation from the mean; 95% in 2 standard deviations.

    Central Limit Theorem

    • A statistical theorem stating that the sampling distribution of the mean approaches a normal distribution as the sample size increases.
    • This is important for statistical tests and estimations.

    Data Analysis Process - Data collection (sampling)

    • A sample is a smaller representative subset of a larger population to avoid sampling the entire population.

    Data Analysis Process - Data Visualization

    • A process enabling the visualization of patterns and insights present in large data sets,
    • Charts, graphs, and similar visual representations are created to showcase different trends present in data sets.

    Machine Learning Models - Supervised learning

    • Predicts a target output based on input data (for example, credit risk in loan applications.).
    • Includes algorithms like Support Vector Machines (SVM), decision trees, k-nearest neighbors (KNN), logistic regression, etc.

    Machine Learning Models - Unsupervised Learning

    • Aims to recognize patterns and relationships within data without needing a pre-defined classification.
    • Includes techniques like clustering (group similar data points), dimensionality reduction (reducing the number of variables), association rules (finding correlations between data points), etc.

    Classification

    • Classification aims at assigning observations into categories.
    • Common algorithms include:
    • k-Nearest Neighbors (k-NN)
    • Decision Trees
    • Support Vector Machines (SVM)
    • Neural Networks (NN)
    • Naive Bayes

    Regression

    • Aims at predicting continuous numerical values. (for example, house prices, salaries).
    • Common algorithms include:
    • Linear Regression
    • Multiple Linear Regression
    • Decision Trees
    • Neural Networks

    Data Analysis - Model evaluation

    • Evaluating model performance includes measuring accuracy, error rate, precision, recall, F1-score, and the area under the ROC curve (AUC)
    • These help gauge how well the model generalizes from training to unseen data.

    Data Analysis - Model Evaluation

    • Measures that consider the importance of each class to be correctly identified, such as precision, recall, F1-score, or Kappa, are considered.

    Data Analysis - Resampling and k-Fold Cross-Validation

    • Techniques repeatedly using different samples of data sets to train and evaluate a model which enables the generalization of the model to unseen data, avoiding overfitting.

    Data Analysis - Leave-one-out Cross-Validation

    • Specialized k-Fold cross-validation technique considering each observation for estimating generalizability, but with high computational cost.

    Data Analysis - Boosting (general)

    • An approach to strengthen weak learners (e.g. decision tree) by re-evaluating the misclassified observations and constructing successive learners.
    • Different types of boosting algorithms are available for regression or classification problems.

    Data Analysis - XGBoost

    • A type of boosting algorithm but with regularization to prevent overfitting or over-complex models.

    Data Analysis - Gradient Boosting (general)

    • Ensembles a series of weak models (e.g., single decision trees.) to enhance performance.
    • Aims is to minimise loss function (e.g., mean squared error (MSE) ) in a iterative approach using a gradient descent method.

    Data Analysis - Gradient descent

    • Gradient descent finds a local minimum of a mathematical function by taking iterative steps (through a pre-defined learning rate) in the descent direction of the function using its gradient.

    Data Analysis - Underfitting

    • The model is too simplified for representing complex data or patterns.
    • Techniques to avoid this are to increase model complexity (adding more features/parameters or making it more complex) and increasing dataset size for model learning.

    Data Analysis - Overfitting

    • The model is too complex and has learned the training data and their noise, not the underlying patterns in the data.
    • To avoid this, improve data quality, increase training data size, and reduce model complexity. Techniques are to increase training data, improve data quality.

    Data Analysis - Bias-Variance Tradeoff

    • A balance concept in model building that strives to minimize both bias and variance.
    • Both high bias and high variance result in poor out-of sample predictions.

    Data Analysis - Quantile-Quantile (Q-Q) Plots

    • Useful to assess whether data follow some particular probability distribution (for example normal distribution).

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