Understanding Bias in Machine Learning

Mehmet Akif Cifci
4 min readFeb 17, 2023

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Bias refers to a tendency or preference towards a particular belief, idea, or outcome that may influence one’s judgment or decision-making in a way that is unfair or inaccurate. Bias can arise from a wide range of factors, such as personal experiences, cultural background, upbringing, education, and social norms.

In the context of research or data analysis, bias can refer to systematic errors or deviations from the true value that can occur in sampling, measurement, or data interpretation. For example, selection bias can occur when the sample used in a study is not representative of the population being studied, leading to inaccurate or misleading results.

1. Bias in machine learning refers to the tendency of an algorithm to produce inaccurate or unfair results because of systematic errors or deviations in the data used to train it. This can happen in a few ways:

2. Data bias: This happens when the training data used to build the algorithm is not representative of the real-world population it is designed to predict. For example, if an algorithm is trained on data that only represents one racial group, it may not be accurate when making predictions about other racial groups.

3. Algorithmic bias: This happens when the algorithm itself is designed in a way that produces biased results. For example, if an algorithm is designed to use income as a predictor of creditworthiness, it may unfairly disadvantage people with lower incomes.

4. User bias: This happens when users of the algorithm (such as humans who use it to make decisions) introduce their own biases into the system. For example, if a hiring algorithm is used by humans who have their own biases, it may reproduce those biases in its recommendations.

→ Bias in machine learning can have serious consequences, particularly in high-stakes applications such as healthcare, criminal justice, and employment. To reduce bias in machine learning, it is important to use representative and diverse training data, carefully design algorithms to avoid discriminatory outcomes and monitor and audit the performance of machine learning systems to identify and correct biases as they arise. Machine learning bias can result from erroneous assumptions made during the data collection, preprocessing, and model training stages of the machine learning process. When these assumptions are based on faulty or incomplete data, or if they reflect the biases of the people who created the algorithm, the result can be an algorithm that produces systematically prejudiced or unfair results. For example, if a facial recognition algorithm is trained on a dataset that includes mostly lighter-skinned faces, it may perform poorly when identifying the faces of darker-skinned people, leading to discriminatory outcomes. Similarly, if an algorithm used to evaluate job applications is trained on data that reflects historical hiring practices that were biased against women or people of color, it may continue to perpetuate those biases, even if the data is no longer relevant or accurate. To address machine-learning bias, it is important to carefully examine the assumptions made throughout the machine-learning process and to be mindful of the potential for biases to be introduced at each stage. It is also important to evaluate the performance of machine learning algorithms in a variety of contexts and to monitor for biases in real-world applications. Techniques such as data augmentation, bias mitigation, and model interpretability can also be used to reduce the impact of bias in machine learning.

Python code for a machine learning model that could be susceptible to bias:

import pandas as pd
from sklearn.model_selection import train_test_split
from sklearn.tree import DecisionTreeClassifier
# Here we load data from a CSV file
data = pd.read_csv('data.csv')

# we split the data into training and test sets
train_data, test_data = train_test_split(data, test_size=0.2)

# here we define the model we want to use
model = DecisionTreeClassifier()

# here we train the model on the training data
model.fit(train_data[['feature1', 'feature2', 'feature3']], train_data['target'])

# here we test the model on the test data
accuracy = model.score(test_data[['feature1', 'feature2', 'feature3']], test_data['target'])

# here we print the accuracy of the model
print('Accuracy:', accuracy)

The code above is an example of building and testing a machine learning model using a decision tree classifier in Python. The code loads data from a CSV file using the pandas library and splits the data into training and test sets using the train_test_split function from sklearn.model_selection module defines the decision tree classifier model using the DecisionTreeClassifier class, trains the model on the training data using the fit method, tests the model on the test data using the scoring method, and prints the accuracy of the model.

However, the code itself does not demonstrate or address the issue of bias in machine learning. To address bias in machine learning, it is important to carefully consider the data used to train the model and to use techniques such as data augmentation, bias mitigation, and model interpretability to reduce the impact of bias.

Bias is a phenomena that favors or opposes an idea by skewing the outcome of an algorithm.
Bias is regarded a systematic mistake that arises in the machine learning model itself as a result of faulty assumptions made throughout the ML process.
Theoretically, bias may be defined as the difference between the average model forecast and the actuality. In addition, it specifies the degree to which the model fits the training data set:
-A model with a greater bias would not closely fit the data set.
-A model with little bias will closely resemble the training data set.

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Mehmet Akif Cifci
Mehmet Akif Cifci

Written by Mehmet Akif Cifci

Mehmet Akif Cifci holds the position of associate professor in the field of computer science in Austria.

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