Machine Learning

Precision vs Recall: How to Use Precision and Recall in Machine Learning - Complete Guide

by
Jon Reilly
,
March 19, 2022

Which is more important: the cost of action or opportunity cost?

This question is at the heart of the debate over precision and recall, two measures of how well an algorithm identifies items in a set. The two measures correspond to different goals: precision is about minimizing the number of false positives, while recall is about maximizing the number of true positives.

In theory, it's possible to optimize for one measure while sacrificing the other. But in practice, most algorithms find a balance between the two measures that depends on the application. In this article, we’ll explore what precision and recall is, how they work in machine learning and AI and how you can use them in your business.

What are precision and recall in ML?

Machine learning is a powerful tool that can be used in many different ways. It can be used to predict customer behavior, optimize marketing campaigns, and much more.

Precision and recall are two important metrics used in evaluating the performance of machine learning models. They are both related to the accuracy of predictions made by the model, but they measure different aspects of it.

Precision measures the percentage of predictions made by the model that are correct. Recall measures the percentage of relevant data points that were correctly identified by the model.

For example, suppose that a spam detection classifier identifies 8 spam emails in a dataset of 12 emails. Of the 8 spam emails predicted, 5 are actually spam, while the rest are not-spam. The precision of this classification model would be 5/8, while the recall would be 5/12. 

In such a relatively "low stakes" use-case, you might be content with such a precision rate, but in a more “high stakes" use-case like cancer diagnosis, you would want a much higher precision rate. The precision-recall tradeoff can be visualized in the confusion matrix, which shows the false positive rate (FPR), true positive rate (TPR), false negative rate (FN), and true negative rate (TN).

A confusion matrix, comparing the predicted class to the true class.

Why should you care about precision and recall?

Machine learning models are designed to make predictions about future events based on past data - so they need to be as accurate as possible. If your model is making lots of incorrect predictions, or failing to identify important data points, then it's not going to be very useful for your business.

Precision and recall are two metrics used to evaluate the performance of a
classification or prediction system. They are both important - you want your classification or prediction system to have high precision and high recall. 

From the business perspective, if you are using machine learning to decide which customers to target with a marketing campaign, you would want a high recall rate, since you want to make sure you are not missing any potential customers. 

How to calculate precision and recall?

Precision and recall are two important measures of how well a set of data matches a given target.

To calculate precision for any binary classification task, you need to know the number of true positives, false positives, and true negatives. True positives are the number of instances that matched the target correctly, false positives are the number of instances that matched the target incorrectly but were counted as true positives, and true negatives are the number of instances that did not match the target correctly.

Precision = (true positives)/(true positives + false positives)

To calculate recall, you need to know the number of true positives, false negatives, and true negatives. True positives are the number of instances that matched the target positive class correctly, false negatives are the number of instances that matched the target incorrectly but were counted as false negatives, and true negatives are the number of instances that did not match the target correctly.

Recall = (true positives)/(true positives + false negatives)

These simple calculations can be very helpful when you are trying to improve your model performance, which is done by going back to the data and ensuring that you have a high-quality dataset that’s representative of the real life problem you’re trying to solve.

How to calculate precision and recall for multi-class classification problems?

Precision and recall can be calculated for multi-class classification problems, but you will need to use a different formula. The precision and recall for multi-class classification problems are calculated using the following formulas:

Precision = (true_positives_1 + true_positives_2 + ... + true_positives_k)/(true_positives_1 + true_positives_2 + ... + true_positives_k) + (false_positives_1 + false_positives_2 + ... + false_positives_k)
Recall = (true_positives_1 + true_positives_2 + ... + true_positives_k)/(true_positives_1 + true_positives_2 + ... + true_positives_k) + (false_negatives_1 + false_negatives_2 + ... + false_negatives_k)

These formulas can be used for any number of classes. In legacy AI systems, data science professionals would calculate these metrics, from recall and precision to the F1 score and visuals like the receiver operating characteristic (ROC) curve. The ROC curve illustrates the predictive value of a binary classifier system, and the area under the curve (AUC) of which summarizes its performance between the precision score and recall score. 

These evaluation metrics would be calculated with tools like Python and Sklearn. Now, with Akkio’s no-code AI flow, any business can automatically gain insights into these metrics with no  technical expertise needed.

How do you improve your machine learning models' precision and recall?

Both precision and recall can be improved with high-quality data, as data is the foundation of any machine learning model. The better the data, the more accurate the predictions will be.

One way to improve precision is to use data that is more specific to the target variable you are trying to predict. For example, if you are trying to predict churn, make sure you are using data from people who have actually churned - not just people who haven't signed up yet.

Another way to improve metrics is to use a more refined data set. This can be done by filtering or cleaning the data set to remove irrelevant or inaccurate data points.

Beyond data quality, it is also important to make sure that your data set has the right features. If you are trying to predict churn, for example, you would want to include data points like plan type, duration, and payment method.

By paying attention to data quality and feature selection, you can improve the precision and recall of your machine learning models. With high-quality data, you can trust your models to make accurate predictions, resulting in better business outcomes.

Once you've got high quality training data, there are lots of things you can do to improve your models' performance. 

Use more data

Generally speaking, the more data you have, the better your precision and recall will be. This is because more data gives you more opportunities to train your algorithm on high-quality examples, which results in more accurate predictions.

There are a few ways to get more data, such as collecting more data, whether through surveys, focus groups or interviews; using more data sources, such as combining data from different departments within your company; and using both public and private data.

Public data is generally easier and cheaper to obtain than private data, but it may not be as accurate. Private data is usually more accurate, but can be expensive and difficult to obtain.

Train longer

The idea of "diminishing returns" is often used when discussing investments and the benefits of additional time or money put into a venture. In the world of machine learning, this phenomenon is also seen when it comes to the increase in precision and recall with longer training times.

As training time is increased, precision and recall generally improve at first. However, after a certain point, the improvements levels off and additional time spent training provides no further benefits.

In order to maximize the benefits of machine learning, it is important to provide a long enough training time so that the system can reach its maximum potential. However, it is also important to avoid overtraining the system, as this can lead to decreased performance and accuracy.

Finding the right balance between long enough training times and avoiding overtraining can be difficult, but with careful monitoring and adjustment, it is possible to improve precision and recall with longer training times.

Tools like Akkio make it easy to test different training time lengths and determine the optimal time for your specific data set and task. With careful monitoring and adjustment, you can improve precision and recall with longer training times.

Use better optimizers

As machine learning algorithms get more sophisticated, the need for better optimization techniques becomes increasingly important. With better optimizers, we can improve both precision and recall, making our models more accurate and efficient.

One popular optimizer is the gradient descent algorithm. This approach involves taking small steps in the direction of the gradient of the loss function, in order to minimize it. While gradient descent is often effective, there are other options that may be even better suited for a particular task.

For example, the Adam optimizer is a variant of gradient descent that has been shown to be more efficient in some cases. It adjusts its parameters more quickly than gradient descent, which can lead to improved performance.

Another popular optimizer is the conjugate gradient algorithm. This approach uses a series of orthogonal directions to find the minimum of a function, which can be helpful when the loss function is not well-understood.

In addition to these well-known optimizers, there are a number of alternate approaches that may be worth exploring. For example, the Bayesian optimization algorithm uses a Bayesian model to determine the best set of parameters for a given problem. This can be a more effective approach than traditional optimization methods, particularly when the number of parameters is high.

With Akkio, the best optimizer for your dataset is automatically selected. This approach can help you to achieve the best performance possible for your task at hand.

How can you apply machine learning and AI to your business? How can you ensure you make accurate predictions?

As AI becomes more prevalent, businesses are looking for ways to incorporate it into their operations. However, many companies don't have the coding skills necessary to create and manage AI algorithms.

No-code AI platforms provide an easy way for businesses to get started with AI. These platforms allow you to create and deploy AI models without any coding experience. No-code AI platforms also make it easy to make accurate predictions. By using pre-built algorithms and libraries, you can quickly build models that can predict outcomes with a high degree of accuracy.

With Akkio, for example, you can create predictive models in minutes by using drag-and-drop tools. And with the help of powerful algorithms and automation, you can achieve accuracies that rival those of hand-coded models.

Akkio automatically calculates and optimizes precision and recall for your data, so you can achieve the most accurate predictions possible. By using many algorithms, libraries, and data pre-processing features, Akkio makes it easy to build complex models that can handle a wide variety of data.

Conclusion

Building accurate predictive models is essential for making the most of artificial intelligence and machine learning. Akkio makes this possible using a no-code platform, which means businesses don't need data scientists to create predictive models.

Precision and recall are two important factors to consider when creating predictive models, and the balance between the two will vary depending on the use case. Akkio employs a number of ways to optimize models for precision and recall, ensuring that businesses can get the most out of their data.

Try a free trial of Akkio to see how the platform can help you automate processes, improve decision-making, predict customer behavior, and more.

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