# How To Evaluate Machine Learning Models

**How To Evaluate Machine Learning Models** – Choosing a machine learning method to build your software is only half the battle. Yes, it is a progressive approach. Yes, it brings automation, the much-discussed machine intelligence and other great benefits. But just because you put it in there is no guarantee that your project will go well and pay off. So how do you measure the success of a machine learning model? Different machine learning models – whether simpler algorithms like decision trees or sophisticated neural networks – require a specific metric or multiple metrics to evaluate their performance. They help you identify your model’s weaknesses early and decide whether the entire ML project is worth the investment and effort you’ve invested.

In this post, we explore the most important machine learning metrics, explain what they are, and provide recommendations on how to track them. Let’s dive in.

## How To Evaluate Machine Learning Models

Before starting with the tests, it is worth recalling the machine learning pipeline to better understand when and why the model needs to be tested and evaluated.

#### The Difference Between Training Data Vs. Test Data In Machine Learning

And measure their performance against unseen (experimental) data using metrics. After comparing the results, you can fine-tune it if it doesn’t work well or send it directly to

On the production data to ensure that it corresponds to the current reality. Performance tests can also be used here to monitor potential damage to the design and capture any dangerous changes so that you can do so.

However, the use of metrics is only possible here if the model used has predictable and well-founded data. For example, consider a demand forecasting model for a taxi service that predicts the number of people requesting a ride downtown on a Friday at 6 p.m. In this case, the service receives the ground truth data at 18 p.m. to check whether the forecast demand matches the actual. But sometimes it is difficult to determine the truth from production data, such as in sentiment analysis or image recognition cases, when users do not always have the opportunity to give feedback.

### Stages Of The Machine Learning (ml) Modeling Cycle

Machine learning benchmarks allow you to estimate the performance of a machine learning model once it has been trained. These numbers give you the answer to the question:

So let’s say you have a simple binary classification task where the model needs to classify data points into blue and orange based on color. This data is in 2D space. To solve this task we can use the simplest

And draw a straight line between the two classes with orange and blue dots outside their class. Or we can choose a more complex method of drawing boundaries between data points using a curved line called a

#### Top 6 Machine Learning Algorithms For Classification

At first glance, the higher order polynomial function seems to be the best model because it stores all the blue symbols on one side and all the orange symbols on the other side.

Instead of using all the data as training data, we will split it into two sets – one for training and one for testing. The model is trained on a labeled dataset where the classes to be predicted are already represented, and the input is mapped to the output (

) By the way, do not confuse the loss function with metrics, because the first one is used to measure the performance of the model during training.

### Create Ml Overview

Then we forget about the training set and evaluate how each model performs on the test data. And this is where things change. The linear model makes only one error, whereas the higher degree polynomial model fails twice, meaning that the former performs better. And you wouldn’t know without trying them.

And then the metrics come into play. Once the model is trained, these tests will help you determine if it is good or not.

There is a whole range of metrics for evaluating ML models in different applications. Most of them can be divided into two groups according to the types of predictions in ML models.

### The Machine Learning Life Cycle Explained

Classification is a type of prediction that is used to extract the variation of results in the form of categories with similar characteristics. For example, such models can produce binary results, such as sorting spam and non-spam emails.

Regression is a form of prediction where the outcome variable is numerical rather than categorical (as opposed to categorical). The results are continuous. For example, it can help predict how long a patient will stay in hospital.

Depending on your use case, using a single metric may not give you the full picture of the problem you’re solving. Therefore, you may want to use some metrics to better evaluate your designs.

### Regression Metrics For Machine Learning

This is an attempt at a joke. In fact, unless the bartender is working part-time as a data scientist, the answer will be the usual:

Well, joking aside, the bars mentioned above are class measurements and the drinks ordered from them are predicted by the actual class values within something known as.

The confusion matrix is a basic parameter that can be used to measure the performance of an ML classification model, but it is not considered a metric. By its nature, it is a two-dimensional table that shows actual values and predicted values. Let’s say we need to create a class that detects patients as sick and healthy.

## Build And Evaluate Machine Learning Models By Using Autoai In Watson Studio On Cloud Pak For Data

What does it show? Accuracy is used to calculate the proportion of correct predictions among the total. This is the number of correct predictions divided by the total number of predictions.

Why use it? Because it is one of the most common classification metrics, accuracy is intuitive and easy to understand and implement: it ranges from 0 to 100 percent or 0 to 1. When working with simple modeling cases, accuracy can be important. Also, you can find it in any ML library like Scikit-learn for any scoring model.

If we take the Health/Patient diagnostic model, out of every 10,000 patients, the model correctly classified 9,000 patients, or 90 percent, or 0.9 if we scale from 0 to 1. So this is our accuracy number.

#### Cross Validation: Evaluating Estimator Performance — Scikit Learn 1.3.2 Documentation

Important to understand. Although the accuracy metric is intuitive, it is highly dependent on the specifics of the data. If the data set is unbalanced (the classes in the set are represented equally), the results are not reliable. For example, in the training set there are 98 percent of samples in class A (healthy patients) and only 2 percent of samples in class B (sick patients). That model can easily give you 98 percent training accuracy just by predicting that every patient is healthy, even if they have a serious disease. It is clear that such erroneous results can have negative consequences as people do not get the medical help they need.

What does it show? Accuracy shows what proportion of all positive predictions were correct. To calculate, divide the number of correct positives (TP) by the total number of positives predicted by the classifier (TP + FP).

Returning to our example: Of all the patients that the model found to be sick, how many were correctly classified? We divide the number of 1,000 patients who are actually sick and likely to be sick by the total number of patients who are sick and diagnosed as sick (1,000) and those who are healthy but diagnosed as sick (800). The accuracy result is 55.7 percent.

## Metrics To Evaluate Classification And Regression Algorithms

Why use it? Accuracy is good for situations where you need or can avoid false positives, but cannot ignore false positives. A common example of this is the example of a spam detector. It’s okay if the trend sends a few spams to the inbox, but sending an important non-spam email to the spam folder (false positive) is even worse.

Important to understand. Accuracy is your most important metric when dealing with unbalanced data. But this is not a panacea because there are cases where false negatives and true negatives should be considered. For example, when it comes to finding out how many people who were really sick were classified as healthy and left without help.

What does it show? Recall shows the fraction of correct predictions among positive predictions that the model could make. To calculate, divide all true positives by the sum of all true positives and false negatives in the data set. In this way, unlike the precision measure described above, recall provides an indication of missed positive predictions.

## Practical Guide To Machine Learning Model Evaluation And Error Metrics

So if you follow the formula, you will get an 83.3 percent correct model prediction of all positive outcomes. The closer the reminder is to 1, the better your style is because you don’t miss any positives.

Why use it? In our example you want to find all sick people, so it’s okay if the example detects some healthy people as sick. You would probably be sent for additional tests, which is annoying but not necessary. But it is even worse when the model finds some patients to be healthy and sends them home without treatment. The recall metric performs better than accuracy in this case because it increases the number of people with diseases who are correctly predicted and receive their treatment.

Important to understand. Also

#### Exercise] Evaluate Machine Learning Models With Yellowbrick

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