Artificial Intelligence

A Guide to Training and Testing Data in Machine Learning

Starting out and not sure what are the best practices while training and testing data? Let's dive into the possible issues and their solutions.

Ostap Zabolotnyy
Ostap ZabolotnyyMarketing Manager
A Guide to Training and Testing Data in Machine Learning

Machine learning (ML) is a branch of artificial intelligence (AI) that uses data and algorithms to replicate real-world scenarios so companies can predict, evaluate, and study human actions and events.

Organizations can use ML to study customer behaviors, identify process and operation-related patterns, and anticipate trends and developments. Many businesses have made machine learning a fundamental element of their business.

The construction of ML algorithms is dependent on how data is collected. Moreover, three categories are most frequently used to categorize the information gathered.

The machine learning method creates algorithms using three data sets: 

⦁ Training data

⦁ Validation data

⦁ Test data

What is Training Data and its Use in Machine Learning?

Training data is used to train a model to predict an expected outcome. So, the algorithm's design focuses on creating the expected or predicted result.

Training data teaches an algorithm to extract relevant aspects of the outcome. It is usually the initial dataset used to program an algorithm on how to use various features, characteristics, and technologies to achieve the desired result.

Learning is a process, not a one-time effort. Humans are natural learners as they learn more from real-life examples. To make a machine understand and learn, they require patterns in data. It is easy for us humans to understand from one or maybe two examples, but the computer needs a lot of models since they work differently than we do. Machines have their language, so to train a machine, it must be done in a way a machine understands, for example, by using structured programming languages.

Take an example, teaching a child to identify a car is fairly easy by showing them an image of a car. In the case of machines, you'll need to show thousands of images of different cars for them to identify a car accurately.

Training Data vs. Test Data: Train/Test Split

Training and test data are essential components of machine learning. Machine learning algorithms learn from data, so having the correct data is critical to building successful models. Training and test data sets help us evaluate our models' performance and provide insights into how they work. 

Let's discuss testing data sets, another concept you should understand when addressing how to train ML models. Training data and test data sets are two distinct yet critical elements of machine learning. While training data is required to educate an ML algorithm, testing data allows you to assess the progress of the algorithm's training and change or optimize it for better results.

In other words, when gathering data to train your algorithm, remember that some data will be needed to evaluate how well the training is going. This means that your data will be split into two parts: training and testing.

The most typical technique for data splitting is classifying 80% of the data as the training data set, and the remaining 20% will make up the testing data set. This is known as Pareto Principle or the "80/20 rule".

Possible Issue While Training the Datasets

Now that we are done with two training and test datasets, a question arises. How do we deal with the errors made by our algorithm while trying to improve during the training process? 

A good training session requires passing the data through our algorithm multiple times, meaning we will get the same patterns each time. To avoid this, we use another dataset to see different patterns in the underprocess data. This only calls for one action to be done. The apparent solution is to split your data set again. This is done only to the training data while designating a part of it for validation. This validation will assist your model in filling in the voids that it might have missed earlier and improve faster.

Always ensure that your test dataset fits the following requirements:

⦁ It is large enough to produce significant statistical findings.

⦁ It represents the entire data set. Thus, avoid selecting a test set with characteristics different from those in the training set.

How Is Training Data Used in Machine Learning?

Machine Learning techniques allow machines to forecast and solve issues based on previous observations or experiences. These are the experiences or observations an algorithm can derive from the training data provided to it. Moreover, ML algorithms can learn and develop independently over time since they're trained with the appropriate training data.

Once the model has been sufficiently trained with the required training data, it is tested using the test data. The entire training and testing procedure can be broken down into three steps, which are as follows:

⦁ Feed: First, we must train the model by giving it training data.

⦁ Define: In Supervised Learning, training data is now tagged with the corresponding outputs, and the model transforms the training data into text vectors or various data features.

⦁ Test: In the final phase, we put the model to the test by feeding it test data or an unfamiliar dataset. This stage ensures that the model is efficiently trained and widely applicable.

Traits of Quality Training Data

It is critical to train the model using high-quality data since an ML model's forecast ability greatly depends on how it has been taught. ML also works with the principle of "Garbage In, Garbage Out." Our model will make predictions based on whatever data we feed it. The following factors should be considered for high-quality training data:


The primary quality of training data should be relevant to the problem being solved. Any data you use should be relevant to the current challenge. For example, if you are developing a model to assess social media data, data should be gathered from various social media platforms such as Twitter, Facebook, and Instagram.


The features of a dataset should always be consistent. That means that all data for a specific problem should come from the same source and have the same qualities.


To guarantee uniformity in the dataset, similar characteristics must always correspond to a similar label.


The training data must be large enough to reflect all the features required to train the model more effectively. The model will be able to learn all of the edge cases with a large dataset.

How Much Training Data Is Required?

The audience often asks this question, and a very honest answer is that it depends.

We don't mean to be vague, but this is the response from most data scientists. This is because the amount of data required is determined by several factors, including

⦁ The complexity of the problem

⦁ The learning algorithm's complexity

In machine learning, it’s safe to say that the more data, the better the model. This is because the more you train your model, the smarter it'll become. However, if your data is properly prepared, follows a basic data prep checklist, and is ready for machine learning, you will still get accurate results. 

How Much Data is Enough for Machine Learning

The training and testing sets should be large enough for the machine to learn. But how much is too much?

Well, That is dependent on the platform. Some machines require at least 1,000 records to construct a model. Yet, the accuracy of the data is critical. The industry follows an unwritten rule to construct a dependable model: use 1,000 poor data plus X number of good ones. For example, 1,000 non-performing loans plus X successfully repaid debts.

Nevertheless, this is only an estimate. The number of documents required for your specific scenario can only be established by evaluating various possibilities. According to some experiences, developing a solid model with only 100 records is feasible, while in certain circumstances, over 30,000 records are required.

Factors affecting the quality of training data

To put it simply, the labeled data will influence how intelligent your model can become. It's similar to how a human only exposed to adolescent-level reading would fail to understand complex, university-level literature.