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Understanding Model Evaluation Metrics: Making Sense of Accuracy and Beyond

Last updated on: 
December 27, 2023
|
by 
Abhinav Rawat
The fast well prepared banner
About The Author!
Abhinav Rawat
Abhinav Rawat
Product Manager at Interview Kickstart. The skilled and experienced mastermind behind several successful product designs for upscaling the ed-tech platforms with an outcome-driven approach for skilled individuals.

Machine learning is all about data and how we handle the data to get the optimal results. Each machine learning project primarily focuses on– "How effectively is the model performing?" Machine learning model evaluation metrics offer the solution, acting as a link across the complexity of algorithms and practical applications. They measure the effectiveness of a model, assisting data scientists and engineers in making reasonable choices on model selection, parameter adjustment, and even project viability.

Here’s what we’ll cover in this article:

  • What Are Machine Learning Model Evaluation Metrics?
  • Why Are Model Evaluation Metrics Important?
  • Choosing The Right Metric For Evaluating Machine Learning Models
  • Accuracy
  • Precision
  • Recall
  • F1 Score
  • Confusion Matrix
  • Auc-Roc
  • Log Loss
  • Jaccard Score
  • Kolmogorov Smirnov Chart
  • Gain And Lift Chart
  • Kickstart Your Machine Learning Journey!
  • FAQs On Machine Learning Model Evaluation Metrics

What are Machine Learning Model Evaluation Metrics?

Evaluation metrics are implemented to assess the efficacy of a machine learning model. Each project must include the evaluation of machine learning models or algorithms. It is important to evaluate a machine learning model's generalization potential, predictive power, and overall proficiency. 

When a machine learning model has been trained, machine learning metrics allow you to measure its efficacy. The question "Is my model doing well?" can be answered using these statistics. They support accurate model testing.

We can determine how effectively a machine learning model adapts to new data using model evaluation metrics that distinguish between adaptive and non-adaptive models. We might increase the complete prediction power of the model ahead of deploying it for production on unknown data by employing multiple measures for performance evaluation. 

Why are Model Evaluation Metrics Important?

Some of the reasons why machine learning model evaluation metrics are needed are as follows: 

  1. By evaluating the efficiency of various models, evaluation metrics might help in the selection of a highly accurate and trustworthy model for a specific scenario.
  2. Evaluation metrics might help us learn about aspects wherein the model is underperforming so that we are able to concentrate on enhancing those areas.
  3. By measuring the model's capacity to produce precise predictions on unobserved data, evaluation metrics may be helpful to our understanding of how well the model performs in the actual world.

Choosing the Right Metric for Evaluating Machine Learning Models

The classification for model evaluation metrics in machine learning is given as follows:

Machine learning model evaluation metrics

Accuracy

It calculates what percentage of the total number of events were accurately expected. While it offers a general impression of accuracy, it may not be the ideal option if the datasets are imbalanced. 

The following formula can be used to calculate accuracy for machine learning evaluation metrics:

Accuracy: (TP + TN) / (TP + TN + FP + FN)

Where

TP = true positive

TN = true negative

FP = false positive

FN = false negative

Precision

Precision focuses on the model's precise forecasts. It measures the percentage of accurate positive predictions amongst the positive predictions. Precision serves as an essential statistic for instances where false positives have had significant effects.

The following formula can be used to calculate precision for machine learning evaluation metrics:

Precision: TP/(TP + FP)

Where

TP = true positive

TN = true negative

FP = false positive

Recall

Recall measures how well a model can identify every important event. It determines the proportion of accurate positive predictions to all true positives. The recall is important in areas like medical evaluation, wherein overlooking positive cases could have negative effects.

The formula of Recall (Sensitivity) for machine learning evaluation metrics is:

Recall: TP / (TP + FN)

Where

TP = true positive

FN = false negative

F1 Score

The F1 score maintains the right balance across recall and precision. It is the harmonic mean of the two that provides a more comprehensive understanding of a model's efficiency, specifically if the classes are imbalanced.

The following formula can be used to calculate the F1 score for machine learning evaluation metrics:

F1 Score: 2 * (Precision * Recall) / (Precision + Recall)

Confusion Matrix

It is also referred to as the "error matrix" and is a tabulated visual illustration of the model's predictions when compared to the labels on the actual truth. In simple terms, it is a classification in a binary matrix of size 2 X 2, where one axis contains true values, and the remaining axis contains predicted values. Every row of the confusion matrix denotes an occurrence in a predicted class. At the same time, every column indicates a certain class's occurrences.

Confusion matrix for classification model evaluation metrics

The dimension of the matrix may vary in proportion to the total number of estimated classes. The confusion matrix is easy to generate. However, beginners may find the terms used to create this matrix confusing. 

AUC-ROC 

The AUC-ROC curve can be used when it's necessary to graph the efficacy of the classification model. It is a well-liked and significant indicator for assessing how effective the classification model is.

The ROC curve is a graph that displays how well a classification model performs at various threshold values. We can see how the relationship between the true positive and the false positive is represented by this curve.

The area under the ROC curve (AUC) is implemented to solve the binary classification challenge. AUC is a measure of the likelihood that the machine learning model would rank a randomly selected positive example greater than a randomly selected negative example.

It assesses the accuracy of the model's predictions without considering the categorization threshold. As it stands, the AUC has an accuracy range of [0, 1]. The higher the value, the more effectively the model performs. 

Log Loss

The most significant statistical classification model evaluation metric is log loss. It evaluates how well the model for classification performs when a probability score between 0 and 1 is used as its prediction input. 

Log loss increases when the projected probability diverges from the real value. Every machine learning model is intended to reduce this value. As a result, a perfect model has a log loss of 0, and a lower log loss is desirable.

Jaccard Score

The Jaccard score is a metric used to compare two distinct sets of data. The score ranges from 0 to 1, with 1 representing the highest. To determine the Jaccard Score, divide the total amount of observations in the two sets by the total amount of observations in each set.

Kolmogorov Smirnov Chart

The Kolmogorov-Smirnov (K-S) chart evaluates how well categorization models function. K-S is a metric for determining how far positive and negative distributions are distinct from one another. The K-S value in the majority of classification models ranges from 0 to 100; the greater the value, the more accurate the model is in differentiating between positive and negative events.

The K-S test can also be used to compare two fundamental one-dimensional likelihood distributions. It is a highly effective method for figuring out whether two samples are considerably distinct from each other.

Gain and Lift Chart

Gain or lift is a measurement of an evaluation model's efficiency that is calculated as a ratio of the outcomes produced irrespective of the model. Lift charts are additionally referred to as cumulative lift charts, which is additionally referred to as gains chart. Gain and lift charts are graphical tools for assessing how well categorization models work. The graph assesses model effectiveness in a subset of the population. The greater the lift, the more effective the model. 

Kickstart your Machine Learning Journey!

Model evaluation metrics serve as a reference point in the machine learning setting, directing us in an appropriate way with methods and datasets. The use of evaluation metrics plays an important role in making sure the model is functioning effectively and economically. Always keep in mind that the correct model evaluation metric is an important aspect in guiding you to models that truly contribute to improvements. If you are intrigued to deep dive into machine learning, Interview Kickstart has designed the perfect machine learning program for you. The course not only includes theory and practicals related to ML but also prepares you to crack any tech interview. Sign up for the webinar today!

FAQs on Machine Learning Model Evaluation Metrics

Q1. What is the difference between MSE and R2 in machine learning?

MSE calculates the mean square difference between the expected and real values to determine how well the model is at predicting future outcomes. Whereas R-squared estimates the percentage of the total variance in the dependent variable that might be predicted by the model's independent variables. 

Q2. What are the two metrics that can be used to evaluate search algorithms?

Recall and precision are two fundamental metrics to evaluate search algorithms.

Q3. What is a good Gini for a model?

Any Gini score above 60% is considered a good model.

Q4. What are examples of evaluation indicators?

The examples of evaluation indicators in machine learning are recall, F1 score, accuracy and precision.

Q5. How much R2 score is good?

A good R2 score is closer to 1. If the score is 1, the model is considered as perfect.

Posted on 
October 6, 2023
AUTHOR

Abhinav Rawat

Product Manager @ Interview Kickstart | Ex-upGrad | BITS Pilani. Working with hiring managers from top companies like Meta, Apple, Google, Amazon etc to build structured interview process BootCamps across domains

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