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Machine Learning Basics for a Newbie
6 Steps of Machine learning Lifecycle Introduction to Predictive Modeling
Introduction to Exploratory Data Analysis & Data Insights Descriptive Statistics Inferential Statistics How to Understand Population Distributions?
Reading Data Files into Python Different Variable Datatypes
Probability for Data Science Basic Concepts of Probability Axioms of Probability Conditional Probability
Central Tendencies for Continuous Variables Spread of Data KDE plots for Continuous Variable Overview of Distribution for Continuous variables Normal Distribution Skewed Distribution Skeweness and Kurtosis Distribution for Continuous Variable
Central Tendencies for Categorical Variables Understanding Discrete Distributions Performing EDA on Categorical Variables
Dealing with Missing Values Understanding Outliers Identifying Outliers in Data Outlier Detection in Python Outliers Detection Using IQR, Z-score, LOF and DBSCAN
Sample and Population Central Limit Theorem Confidence Interval and Margin of Error
Bivariate Analysis Introduction
Covariance Pearson Correlation Spearman's Correlation & Kendall's Tau Correlation versus Causation Tabular and Graphical methods for Bivariate Analysis Performing Bivariate Analysis on Continuous-Continuous Variables
Tabular and Graphical methods for Continuous-Categorical Variables Introduction to Hypothesis Testing P-value Two sample Z-test T-test T-test vs Z-test Performing Bivariate Analysis on Continuous-Catagorical variables
Chi-Squares Test Bivariate Analysis on Categorical Categorical Variables
Multivariate Analysis A Comprehensive Guide to Data Exploration The Data Science behind IPL
Supervised Learning vs Unsupervised Learning Reinforcement Learning Generative and Descriminative Models Parametric and Non Parametric model
Machine Learning Pipeline Preparing Dataset Build a Benchmark Model: Regression Build a Benchmark Model: Classification
Evaluation Metrics for Machine Learning Everyone should know Confusion Matrix Accuracy Precision and Recall AUC-ROC Log Loss R2 and Adjusted R2
Dealing with Missing Values Replacing Missing Values Imputing Missing Values in Data Working with Categorical Variables Working with Outliers Preprocessing Data for Model Building
Understanding Cost Function Understanding Gradient Descent Math Behind Gradient Descent Assumptions of Linear Regression Implement Linear Regression from Scratch Train Linear Regression in Python Implementing Linear Regression in R Diagnosing Residual Plots in Linear Regression Models Generalized Linear Models Introduction to Logistic Regression Odds Ratio Implementing Logistic Regression from Scratch Introduction to Scikit-learn in Python Train Logistic Regression in python Multiclass using Logistic Regression How to use Multinomial and Ordinal Logistic Regression in R ? Challenges with Linear Regression Introduction to Regularisation Implementing Regularisation Ridge Regression Lasso Regression
Introduction to K Nearest Neighbours Determining the Right Value of K in KNN Implement KNN from Scratch Implement KNN in Python
Bias Variance Tradeoff Introduction to Overfitting and Underfitting Visualizing Overfitting and Underfitting Selecting the Right Model What is Validation? Hold-Out Validation Understanding K Fold Cross Validation
Introduction to Feature Selection Feature Selection Algorithms Missing Value Ratio Low Variance Filter High Correlation Filter Backward Feature Elimination Forward Feature Selection Implement Feature Selection in Python Implement Feature Selection in R
Introduction to Decision Tree Purity in Decision Tree Terminologies Related to Decision Tree How to Select Best Split Point in Decision Tree? Chi-Squares Information Gain Reduction in Variance Optimizing Performance of Decision Tree Train Decision Tree using Scikit Learn Pruning of Decision Trees
Introduction to Feature Engineering Feature Transformation Feature Scaling Feature Engineering Frequency Encoding Automated Feature Engineering: Feature Tools
Introduction to Naive Bayes Conditional Probability and Bayes Theorem Introduction to Bayesian Adjustment Rating: The Incredible Concept Behind Online Ratings! Working of Naive Bayes Math behind Naive Bayes Types of Naive Bayes Implementation of Naive Bayes
Understanding how to solve Multiclass and Multilabled Classification Problem Evaluation Metrics: Multi Class Classification
Introduction to Ensemble Techniques Basic Ensemble Techniques Implementing Basic Ensemble Techniques Finding Optimal Weights of Ensemble Learner using Neural Network Why Ensemble Models Work well?
Introduction to Stacking Implementing Stacking Variants of Stacking Implementing Variants of Stacking Introduction to Blending Bootstrap Sampling Introduction to Random Sampling Hyper-parameters of Random Forest Implementing Random Forest Out-of-Bag (OOB) Score in the Random Forest IPL Team Win Prediction Project Using Machine Learning Introduction to Boosting Gradient Boosting Algorithm Math behind GBM Implementing GBM in python Regularized Greedy Forests Extreme Gradient Boosting Implementing XGBM in python Tuning Hyperparameters of XGBoost in Python Implement XGBM in R/H2O Adaptive Boosting Implementing Adaptive Boosing LightGBM Implementing LightGBM in Python Catboost Implementing Catboost in Python
Different Hyperparameter Tuning methods Implementing Different Hyperparameter Tuning methods GridsearchCV RandomizedsearchCV Bayesian Optimization for Hyperparameter Tuning Hyperopt
Understanding SVM Algorithm SVM Kernels In-depth Intuition and Practical Implementation SVM Kernel Tricks Kernels and Hyperparameters in SVM Implementing SVM from Scratch in Python and R
Introduction to Principal Component Analysis Steps to Perform Principal Compound Analysis Computation of Covariance Matrix Finding Eigenvectors and Eigenvalues Implementing PCA in python Visualizing PCA A Brief Introduction to Linear Discriminant Analysis Introduction to Factor Analysis
Introduction to Clustering Applications of Clustering Evaluation Metrics for Clustering Understanding K-Means Implementation of K-Means in Python Implementation of K-Means in R Choosing Right Value for K Profiling Market Segments using K-Means Clustering Hierarchical Clustering Implementation of Hierarchial Clustering DBSCAN Defining Similarity between clusters Build Better and Accurate Clusters with Gaussian Mixture Models
Understand Basics of Recommendation Engine with Case Study
8 Ways to Improve Accuracy of Machine Learning Models
Introduction to Dask Working with CuML
Introduction to Machine Learning Interpretability Framework and Interpretable Models model Agnostic Methods for Interpretability Implementing Interpretable Model Understanding SHAP Out-of-Core ML Introduction to Interpretable Machine Learning Models Model Agnostic Methods for Interpretability Game Theory & Shapley Values
Introduction to Machine Learning Interpretability Framework and Interpretable Models model Agnostic Methods for Interpretability Implementing Interpretable Model Understanding SHAP Out-of-Core ML Introduction to Interpretable Machine Learning Models Model Agnostic Methods for Interpretability Game Theory & Shapley Values
Introduction to AutoML Implementation of MLBox Introduction to PyCaret TPOT Auto-Sklearn EvalML
Pickle and Joblib Introduction to Model Deployment
Deploying Machine Learning Model using Streamlit Deploying ML Models in Docker Deploy Using Streamlit Deploy on Heroku Deploy Using Netlify Introduction to Amazon Sagemaker Setting up Amazon SageMaker Using SageMaker Endpoint to Generate Inference Deploy on Microsoft Azure Cloud Introduction to Flask for Model Deploying ML model using Flask
Model Deployment in Android Model Deployment in Iphone

A Quick Guide to Error Analysis for Machine Learning Classification Models

ASHWINI
ASHWINI Last Updated : 18 Aug, 2023
6 min read

This article was published as a part of the Data Science Blogathon

Let’s start with the basics…

What are the objectives an ML model training step is aiming at?

Developing any ML model’s objective is to make them generalizable, reliable, robust (applicable in various scenarios), and have the least bias. As all model algorithms rely on creating an as close version of ground truth as possible – Error Analysis and corresponding actions play a key role in accomplishing this.

ML models have primarily been tested and developed based on single or aggregate metrics like accuracy, precision, recall that cover the model performance on the entire dataset. It does help to tune the overall model performance achieved through further tweaking the algorithms but does not dive into the specifics of the errors to help better resolve the training/test set errors. An in-depth review of the error cases can help systematically arrive at ideas and recommendations to improve the model performance and be as close to the ground truth as possible. Also, error analysis helps to create Responsible ML models by helping identify if the model is behaving more erroneously for certain protected variables/classes.

ML classification models have been used as a case in this article to explain the process better. It is assumed that readers understand the ML model development process in general.

The following is structured per below:

1. What is error analysis in ML?

2. Error Identification and Diagnostics: How and where are the errors distributed for ML classification models?

3. Approach and recommendations for error resolution

1. What is Error Analysis?

Error analysis is the process to isolate, observe and diagnose erroneous ML predictions thereby helping understand pockets of high and low performance of the model. When it is said that “the model accuracy is 90%” it might not be uniform across subgroups of data and there might be some input conditions which the model fails more. So, it is the next step from aggregate metrics to a more in-depth review of model errors for improvement.

An example might be that a dog detection image recognition model might be doing better for dogs in an outdoor setting but not so good in low-lit indoor settings. Of course, this might be due to skewed datasets and error analysis helps identify if such cases impact model performance. The below illustration provides a view of how moving from aggregate to group-wise errors provides a better picture of model performance.

What is Error Analysis

Source: Responsible ML with error analysis

2. Error Identification and Diagnosis

This helps know how errors are distributed across key hypotheses or key features/classes/cohorts of the dataset. For example, in a loan approval model used by a bank, it might be that the model is giving more errors on the individuals who are younger and have a low monthly average balance with the bank.

A. How to do this (manually) especially in case your data is image, voice, or text where you might not have apparent features.

Let us take another example – a favorite one – A cat-classifier! Suppose we train a model on 4000 images (Some having cats) in different settings and test using 1000 images. We find that the model accuracy is 85% (meaning 850 of the 1000 images were predicted correctly!) and 150 images were wrongly tagged.

Sample of Images with Erroneous Classification in Cat-classifier

Error Identification and analysis

Source: http://www.xavierdupre.fr/app/mlinsights/helpsphinx/notebooks/search_images_keras.html

On making a confusion matrix it looks like below:

Error Identification and analysis matrix

Source: Created by the author

But it does not help understand what is being misclassified, so we isolate the 70 and 80 images respectively, so we look at the images that have been misclassified and create some hypotheses/observations on grouping these errors.

On reviewing all examples quickly, we identify that the following seems to be common across all erroneous cases:

1. White cats not being correctly identified

2. Dogs like cats being identified as cats

3. Dark background leads to misclassification and so on

The hypothesis or commonalities observation for all erroneous use cases is followed by creating a table in Excel or a similar tool to map the exact distribution of the errors. For our cat classification example it looks like below (please note that each data point/image might have more than one of the below tags) :

model error distribution Error Identification and analysis

Source: Created by the author

* for image classification it might be difficult to get this column but can we have done for other use cases like credit approval models

B. Is there a way to do this more automatically? In case the data has more apparent features like a credit rating model, product recommendation model or customer churn model uses cases – a package for quick identification is erroranalysis.ai. It can help identify and further diagnose the error distribution across features and certain values of those features. We can create Heatmaps and TreeMaps to show what is causing the errors and further details on the error specifics.

An example for income prediction on tabular UCI Census Income dataset is given below:

UCI

Source: Responsible ML for error analysis

responsible ML

Source: Responsible ML for error analysis

Once the errors have been identified the respective variables can be diagnosed further to get details of the error cohort it is more prevalent in – for this example below is the diagnostics for higher education_num the difference betweenAs all model algorithms rely on creating an as close version of ground truth as possible – Error Analysis and corresponding actions play a key role in accomplishing this. higher income (orange) lower (blue) is different from other group cohorts.

3

Source: Responsible ML for error analysis

3. Approach and recommendations for error resolution

After identifying and analyzing the errors per above, we need to move to the next step of resolving them!

Let us use a speech recognition example, we populate the similar table mentioned above with additional columns that are the overall % of such cases with error and then the overall % of the dataset that is impacted by the error. It makes sense to choose and start from the hypothesis that would impact the most cases being impacted (also further explained in Andrew Ng’s video).

3. Approach and recommendations for error resolution

Source: Adapted from https://www.coursera.org/learn/introduction-to-machine-learning-in-production/lecture/6kFkv/prioritizing-what-to-work-on

The above example makes sense to start working on People noise/ Clean Data tag data correction first to have the most impact.

After choosing the area(s) the following can be tried basis feasibility, efforts needed, the importance of improvement in that area, and most accuracy that can be achieved in that area:

1. Collecting more data points for the cases where errors are happening

2. Augmentation of data or steps to improve data quality

3. Use other ML models /tune hyperparameters differently

Frequently Asked Questions

Q1. What are the classification errors?

A. Classification errors refer to instances in machine learning where a model incorrectly assigns a data point to the wrong class or category. These errors can be false positives (misclassifying something as belonging to a class when it doesn’t) or false negatives (failing to classify something correctly). Reducing classification errors is crucial for enhancing model accuracy and performance.

Q2. What are the types of errors in machine learning?

A. There are two types of errors in machine learning models: Reducible Errors and Irreducible Errors.
1. Reducible Errors: These errors are caused by shortcomings in the model itself, such as inadequate feature representation, incorrect assumptions, or suboptimal algorithms. Reducible errors can be minimized through model improvement, fine-tuning, better feature engineering, and refining the learning process.
2. Irreducible Errors: These errors stem from factors that are beyond the control of the model and the data scientists, such as inherent variability in the data or unpredictability in the underlying phenomena being modeled. They represent a limit to how well the model can perform, even with perfect feature representation and algorithm selection. Irreducible errors are challenging to eliminate since they arise from inherent uncertainties in the real world.

While reducible errors can be addressed through model optimization, irreducible errors are a fundamental limitation in the modeling process and cannot be completely eliminated due to the complexity and noise present in real-world data.

Closing thoughts:

Just like model design and testing Error Analysis is an iterative process so it might be worthwhile to spend time and distribute it across the team to conquer it faster.

Article by Ashwini Kumar | Data Science Lead & Crusader | Linkedin

The media shown in this article are not owned by Analytics Vidhya and are used at the Author’s discretion.

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ASHWINI
ASHWINI

Analytics & Data Science Leader | Applies analytics in Retail, Communications & Media domain across marketing, Omni channel sales, operations and people management functions| Helps convert Business Strategy to Data Strategy

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