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Common Mistakes to Avoid in Fuzzy Data Matching and How to Fix Them

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Farah Kim • March,2023

As important as fuzzy data matching is, it is a complicated and daunting task. Even the most experienced data engineers will have difficulty developing and testing fuzzy data-matching algorithms to detect hidden errors. They can be prone to mistakes that can lead to an unusually high number of false positives or negatives. Worse, it could also cause the whole project to fail, forcing a complete reset, where you would have to start from scratch. 

Whether you’re using a codeless fuzzy data-matching solution or a manual method, you must be careful of common mistakes that could cause significant challenges for the business. 

In this section, we’ll discuss four of these errors, with examples, and strategies to avoid them.

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Insufficient Pre-processing or Data Cleaning

Data cleansing is a necessary pre-requisite for an accurate fuzzy match resolution. The more refined a data cleansing process, the better the outcome. 


For example, seemingly minor issues like punctuation or stop words (the, is, and) can greatly affect a fuzzy match process. Removing stop words can significantly reduce false matches. 


Similarly, Another common preprocessing mistake is failing to consider the cultural context of the data. For example, if you are matching names, it’s essential to consider the cultural context, as some cultures use different naming conventions. For instance, in some cultures, the surname comes before the first name, while in others, it’s the opposite. 


How to prevent the mistake from happening:


To overcome this challenge, it’s crucial to have a thorough understanding of the cultural context of the data. This can involve researching naming conventions and patterns in different cultures, as well as consulting with subject matter experts. Additionally, you can use a fuzzy matching solution like WinPure to save these variations so it can be easier and faster to identify patterns in the data and improve preprocessing for better matching accuracy.


Another common preprocessing mistake to avoid is failing to consider the data’s context. For example, matching addresses can be complicated due to variations in formatting and abbreviations. Preprocessing should involve standardizing the data to a consistent format and removing irrelevant information such as zip codes or apartment numbers. You can easily do this through the use of regular expressions, which are a powerful tool for identifying and manipulating patterns in text data. 


It is best practice to proceed with fuzzy matching only when you’re confident with the quality of your data. 


Overlooking Common Variations in Data

You might think differences in upper and lower case variations won’t affect an analysis outcome, but the fact is, variations in data can result in incorrect matching or grouping of records. 


For example, if a dataset has a person’s name listed as “John Smith” in some records and “john smith” in others, a fuzzy matching algorithm that doesn’t account for case sensitivity might consider these two as separate entities, resulting in duplicate or incorrect matches.


Similarly, if a dataset has a field for a product name, and some records list the name in all caps while others list it in mixed case, a grouping or aggregation function might not correctly group all the records for the same product together, resulting in incorrect analysis or reporting.


How to avoid making this mistake: 


Variations in data is as bad as missing, invalid, or incorrect data. You must standardize data into a consistent format so the match process can be done efficiently. Data standardization can be done either using a data preparation tool like WinPure, or through manual methods such as using Excel formulas to correct variations. 


Additionally, you can also make use of data dictionaries, which are a collection of standardized terms and definitions for specific fields, to ensure consistent representation of data across different sources. This helps to reduce the likelihood of variation in the data and improve the accuracy of fuzzy matching.

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Using the Wrong Fuzzy Matching Techniques

As mentioned in the Fuzzy Matching Guide, this process combines different techniques. Depending on the type of data you’re processing, you will need to identify the correct fuzzy matching technique. Using the wrong technique can cause your project to fail! 


For example, a data analyst might use the Levenshtein distance algorithm to measure similarities between two strings; however, if they are faced with strings that have semantic differences, such as “Dr. John Smith” and “John Smith, MD”, the Levenshtein distance is the wrong fuzzy matching technique to use. 


Instead, you would have to combine fuzzy matching and entity resolution techniques to consolidate these two strings as one version of the truth. 


Fuzzy string matching techniques, such as the Jaro-Winkler distance or cosine similarity, can capture similarities between the two strings based on character-level differences, while entity resolution techniques can use domain-specific knowledge to recognize that “Dr.” and “MD” refer to the same entity.


For instance, one possible approach would be to use a pre-processing step to standardize the titles and abbreviations in the strings, such as replacing “Dr.” with “Doctor” and “MD” with “Medical Doctor”. Then, a fuzzy string matching technique could be used to compare the standardized strings and compute a similarity score.


Finally, an entity resolution algorithm could be applied to the results of the fuzzy string matching to identify the most likely match. This approach takes into account both the individual character-level differences between the strings and the domain-specific knowledge about the titles and abbreviations commonly used in the medical profession.


How to avoid making this mistake: 


Always test and compare the performance of multiple techniques on a sample of the data before selecting the best one. Using a comprehensive fuzzy matching solution that incorporates multiple techniques and allows for easy comparison and selection can also be beneficial. Regularly reviewing and updating the fuzzy matching process to account for changes in the data and ensuring that the matching parameters are appropriate for the specific use case can help to avoid this mistake.

Implementing Inappropriate Thresholds

Thresholds are values used to determine whether the similarity score between two strings is high enough to consider them a match. Setting thresholds too high may result in missed matches, while setting them too low may result in false matches. 

For example, you have two records: 


Record 1: “John Smith”

Record 2: “John Smithe”


Suppose we want to match these records based on their name similarity. We can use a similarity metric such as the Jaro-Winkler distance to compute the similarity score between the two records.


Suppose we set a threshold of 0.9 to consider two records a match. If we apply this threshold to the example, we would conclude that the two records are not a match since their Jaro-Winkler distance is 0.89, which is below the threshold. This would result in a missed match.


On the other hand, if we set the threshold too low, say 0.6, we would consider the two records a match since their Jaro-Winkler distance is above the threshold. However, this would result in a false match, as “John Smithe” is not actually the same as “John Smith”.


Therefore, it is important to select an appropriate threshold value that balances the trade-off between missed matches and false matches based on the data’s specific use case and characteristics.


How to avoid making this mistake: 


To determine an appropriate threshold, you can experiment with different values and evaluate the impact on the matching results. When using a fuzzy matching solution like WinPure, setting the threshold can be done faster and more efficiently because the software typically provides a user-friendly interface for selecting and fine-tuning the threshold value.


For example, WinPure’s fuzzy matching software allows you to adjust the threshold value through a slider bar or by entering a specific value. The software also provides real-time feedback on the number of matches and non-matches as you adjust the threshold value. This enables you to quickly find the optimal threshold value for your data and use case without having to manually compute similarity scores and evaluate them one by one.

Improper Handling of Multiple Fields

When merging data from multiple sources, you may have to deal with multiple identifier fields. For example, you are trying to match customer records from two different sources – one source provides name and address information, while the other source provides name, email, and phone number information. If you only match based on name and address, you may miss potential matches that have slightly different address information or use a different email or phone number. 


On the other hand, if you only match based on email and phone number, you may miss potential matches that have slightly different name or address information.


Here’s an example table comparing the results of fuzzy matching with and without considering multiple fields:


Record ID Name Address Email Phone
1 John Doe 123 Main St. (555) 555-1234
2 Jon Doe 123 Main Street (555) 555-1234
3 Jane Smith 456 Maple Ave. (555) 555-5678
4 John Doe 1234 Elm St. (555) 555-1234
5 Jane Smyth 456 Maple Avenue (555) 555-5678


If we only consider name and address for fuzzy matching, we may miss potential matches between records 1 and 2, as well as between records 3 and 5:

Record ID 1 Record ID 2 Fuzzy Match Score
1 2 0.933
2 1 0.933
3 5 0.9
5 3 0.9


However, if we also consider email and phone number fields for fuzzy matching, we can accurately match all the records:

Record ID 1 Record ID 2 Fuzzy Match Score
1 2 1.0
2 1 1.0
3 5 1.0
4 1 0.727
5 3 1.0


As you can see, considering multiple fields for fuzzy matching can significantly improve the accuracy of matching and reduce the chances of missing potential matches.

How to avoid making this mistake: 

Before running the match, you must determine which fields are the most accurate, important, and relevant and prioritize them accordingly. You could determine this during the data cleansing phase, where you’re verifying and validating the quality of your data. Additionally, you can use machine learning techniques such as classification or clustering to identify which fields are most relevant for matching.

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Ignoring the Human Element

It is an industry mistake to be over-reliant on automated techniques and solutions. You need human intervention and intuition to understand and make decisions about the data during the pre-processing and after the matching stages. For example, in the pre-processing stage, you may discover you have 10% invalid or obsolete phone numbers of your customers. With this knowledge, you may not want to use phone numbers as a primary component in the data matching process. 


Similarly, fuzzy matching can produce false positives or false negatives, which can negatively impact downstream processes such as data analysis or data integration. These situations need the insight and expertise of subject matter experts or data owners. Ignoring this human element leaves your business vulnerable to costly mistakes, lawsuits, and other penalties. 

How to avoid making this mistake: 

Provide a structured process and avoid overwhelming yourself and your team with vast amounts of data to process. Start small, set protocols, work on a sample data, then replicate the methods on the data set. Remember, your teams need to have the time to make intuitive decisions – which can only happen if 80% of their time is not spent in fixing data! 

Relying Only on Manual Methods

We know most professionals choose to opt for manual fuzzy data matching since it offers accuracy and control. However, considering the complex nature of data today, it would be unwise to rely on manual methods alone. Not only are they time-consuming, but  are also error-prone. 


How to avoid this mistake: 


Your best bet is to move towards codeless fuzzy matching solutions that use machine learning algorithms to automate the matching process. These solutions can quickly and accurately identify matches, even in large and complex datasets, without the need for manual intervention.


By using codeless fuzzy matching solutions, data professionals can improve their matching accuracy while saving time and resources. Additionally, these solutions can be customized to specific business needs and data types, ensuring that the matching process is tailored to the unique requirements of each project.


To conclude, fuzzy data matching is a challenging task, requiring you to make careful decisions about factors such as preprocessing techniques, understanding common variations in data, overfitting, inappropriate thresholds, inadequate handling of multiple fields, ignoring the human element, and so on. 


For a successful fuzzy matching process, it’s necessary to use a combination of tools, human intuition, and the application of data quality guidelines. By avoiding these mistakes and incorporating the right strategies and tools, professionals can achieve accurate and efficient fuzzy data matching without relying solely on manual methods or multiple fuzzy matching techniques.

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Farah Kim


Farah Kim is a human-centric product marketer and specializes in simplifying complex information into actionable insights for the WinPure audience. She holds a BS degree in Computer Science, followed by two post-grad degrees specializing in Linguistics and Media Communications. She works with the WinPure team to create awareness on a no-code solution for solving complex tasks like data matching, data deduplication, and MDM.

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