What is Data Preprocessing? - Definition, Importance, & Steps

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May 10, 2023

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Data Preprocessing in Data Science is a crucial step in the workflow that involves cleaning, transforming, and preparing raw data into a format suitable for analysis. The quality of the data used in analysis directly affects the accuracy and reliability of the results, making data preprocessing an essential task for any Data Science project. Data Preprocessing also makes your data suitable for data mining. The Data Preprocessing technique is used in the initial stages of AI development and Machine Learning. With proper Data Science training, you can learn about Data Preprocessing and manage huge chunks of data.

What is Data Preprocessing?

Data preprocessing, often used in data mining and data analysis, takes the raw data and processes it into a format that can be understood and analysed by computers and Machine Learning models.

Raw data is often collected from various sources in different formats and may contain errors, inconsistencies, or missing values that need to be addressed before analysis. Data Preprocessing in Data Science is important as the quality of the data used in analysis directly affects the accuracy and reliability of the results.

So, professionals with Data Science training would be able to clean and transform raw data and can ensure that the data used in the analysis is accurate and reliable, leading to more accurate insights and better decision-making.

What are the common problems found in raw data?

Raw data, or data collected from various sources, can have many problems that make it difficult to use for analysis. Here are some of the common problems that Data Preprocessing addresses in raw data:

  1. Missing Data: Raw data may contain missing values, which can be due to various reasons such as data entry errors or system issues.
  2. Inaccurate Data: Raw data may contain errors, inconsistencies, or inaccuracies, which can occur due to several reasons such as human error, measurement error, or technical issues.
  3. Outliers: Outliers are data points that deviate significantly from the majority of the data points. Outliers can occur due to measurement errors, data entry errors, or unusual circumstances.
  4. Duplicates: Raw data may contain duplicates, which can occur due to data entry errors or technical issues.
  5. Inconsistent Data: Raw data may contain inconsistent data, which can be due to differences in data formats or standards used in different sources.
  6. Non-standard Data: Raw data may be in non-standard formats or data types that are not suitable for analysis.

These issues can affect the quality of the data used in the analysis, and data preprocessing in data science is required to address these issues before the data can be used for analysis. By identifying and correcting these issues, Data Scientists can ensure that the data used in the analysis is accurate, reliable, and suitable for analysis.

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Steps in Data Preprocessing

After understanding Data Preprocessing, let’s look at the steps in data preprocessing in detail.

  • Data profiling

Data profiling is the first step in Data Preprocessing. This involves examining, analysing, and reviewing the collected data for its quality. This step starts with identifying different data sets that are relevant to the project and then preparing the inventories for the significant attributes. This helps to form a hypothesis that would help in data analysis or making the Machine Learning task easier.

Data profiling helps to connect the data sources to their relevant business concepts. It helps to analyse which preprocessing libraries could be used. 

  • Data cleansing

The second step of Data Preprocessing in Data Science is Data cleansing. The objective of this process is to identify an easier way to correct quality issues. This is done by removing bad data and providing the missing data. This makes the raw data suitable for Machine Learning projects.

The professionals with the Data Science certification course are trained to work on different types of raw data. This would help them to prepare for major projects in the professional world. With data cleansing, the raw data gets prepared for further analysis.

  • Data reduction

There are many bits of raw data that are not required for your computation in Machine Learning, Artificial Intelligence or any type of analytical task. This process removes the data that are not required for the particular project.

The process of data reduction uses techniques like Principal Component Analysis. This helps to change the raw data into a simple form that the system can easily understand, process and analyse. With proper Data Science training, the professional can use different data reduction techniques for the project.

  • Data transformation

Data transformation helps the Data Scientists analyse how the data can be organised in different aspects to make it more relatable to the goal. This includes structuring the unstructured data, merging the required variables and identifying the important ranges. This would help the Data Scientists to focus on the data in a proper way.

  • Data Enrichment

One important step of Data Preprocessing in Data Science is data enrichment. Data Scientists use different features of engineering libraries to the raw data to get their desired transformations.

Data enrichment arranges the data to achieve the optimised balance between the training time for the new model and the time required for computation. Data Scientists spend a considerable amount of time on it so that the data received after Data enrichment would help them in their project.

  • Data validation 

Data validation is the last step of Data Preprocessing. In this process, the data is split into two different sets. The first set trains the Machine Learning or the Deep Learning model. The second set is used to test the data and used to analyse the accuracy and the robustness of the particular model. 

For professionals with Data Science training, working on data validation is important as it helps to identify the problem in the hypothesis. If the Data Scientists are happy with the results after data validation, then the processed data is forwarded to the Data Engineering team, which analyses how to scale up the data for production.

When you are trying to understand Data Preprocessing, knowing about the steps in Data Preprocessing is equally important. These steps would help the Data Scientists to provide processed data for further operations.

Importance of Data Preprocessing

Data Preprocessing has been playing an important role in Data Science. Without it, any analysis would not yield the proper results. Let’s look at the importance of Data Preprocessing.

  • Improves reliability and accuracy

As discussed, preprocessing the data helps in removing unwanted and inconsistent data that results from any errors. Removing those data improves the accuracy, reliability and quality of the data set. 

  • Data Preprocessing in Data Science

provides the system with processed and reliable data. This would help to improvise the efficiency of the system and provide more accurate results.

  • Enhances Data algorithm’s readability

Professionals with Data Science training use Data Preprocessing to improve the data to such an extent that it makes it easier for the Machine Learning algorithms to understand, analyse and process it.

  • Provides consistent data

When the unwanted data is removed from the pile of data, you are left with the quality data that would help in providing accurate results. When the data is cleaned through Data Preprocessing, it helps to streamline the process. A ‘Data-driven’ decision can only prove to be beneficial if the data is properly processed before being analysed.

  • Removes duplicity

Data Preprocessing helps to remove duplicate data from a dataset. If the system analyses the repeated data, the results might vary. This would affect the entire project. So, it is important to remove duplicity, which can be easily done through Data Preprocessing

  • Identify and sort missing data

When the raw and uncompiled data is preprocessed, there would be instances of missing data. Data Preprocessing in Data Science helps to identify missing data. It also helps to sort the missing data by providing the required data. This would help in proper data analysis.

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Data Preprocessing plays an important role in Data Science. Without Data Preprocessing in Data Science, Data Scientists can't separate unwanted and inconsistent data from the required data. It helps to enhance the results, as the system would process quality data. As a professional looking to develop newer skills and certifications in Data Science, I would highly recommend exploring the Data Science Certification Course offered by StarAgile. As a facilitator for professionals to bridge their knowledge gaps, StarAgile consistently expands its course portfolio to meet global requirements and address evolving learning needs.


1. What are some common techniques used in data preprocessing?

Some common techniques used in data preprocessing include data cleaning, data transformation, feature scaling, and feature encoding. Data cleaning involves removing or correcting errors in the data, while data transformation involves converting data into a more useful format. Feature scaling involves scaling data so that all features are on a similar scale, while feature encoding involves converting categorical variables into numerical values.

2. What are some tools used for data preprocessing?

There are many tools available for data preprocessing, including programming languages like Python and R, as well as specialized software like Excel and OpenRefine. There are also libraries and packages available for these programming languages that can make data preprocessing easier and more efficient.

3. What are the challenges in data preprocessing?

One of the main challenges in data preprocessing is dealing with missing data. This can be especially problematic if there is a large amount of missing data or if the missing data is not random. Other challenges can include dealing with outliers, handling noisy data, and selecting appropriate data transformation techniques.

4. How does data preprocessing fit into the overall data analysis process?

Data preprocessing is an important step in the overall data analysis process. Once the data has been cleaned and transformed, it can be used for exploratory data analysis, model building, and other types of analysis. By ensuring that the data is in a usable format, data preprocessing can help to improve the accuracy and reliability of the analysis.

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