Auditing Mannequin Bias with Balanced Datasets with Mimesis

# Introduction

Whether or not they’re well-established classifiers or state-of-the-art huge fashions like massive language fashions (LLMs), constructing machine studying options typically entails a threat: algorithms may silently undertake prejudices inherent within the historic coaching dataset they have been educated on. However in a high-stakes situation or one the place knowledge is delicate, how can we audit whether or not a mannequin is biased with out compromising real-world info?

This hands-on article guides you in coaching a easy classification mannequin for “mortgage approval” on biased knowledge. Primarily based on this, we are going to use Mimesis, an open-source library that may assist generate a wonderfully balanced, counterfactual dataset. You can check “pretend” customers with equivalent monetary backgrounds however totally different demographic traits, thereby figuring out whether or not the mannequin discriminates in opposition to sure teams or not.

# Step-by-Step Information

Begin by putting in the Mimesis library in case you are new to utilizing it, or you might be engaged on a cloud pocket book atmosphere like Colab:

Earlier than auditing a mannequin, we really must get one! On this instance, we are going to synthetically generate a dataset of 1,000 financial institution clients, with simply two options: gender and revenue. These options are categorical and numerical, respectively. The info creation shall be deliberately manipulated in order that the gender attribute unfairly influences the binary end result: mortgage approval. Particularly, for labeling the dataset, we are going to contemplate a situation through which males are usually permitted, whereas ladies are solely permitted once they have remarkably excessive revenue.

The method to create this clearly biased dataset and prepare a choice tree classifier on it’s proven under:

import pandas as pd
import numpy as np
from sklearn.tree import DecisionTreeClassifier

# 1. Simulating biased historic knowledge (1000 cases)
np.random.seed(42)
n_train = 1000
genders = np.random.selection(['Male', 'Female'], n_train)
incomes = np.random.randint(30000, 120000, n_train)

approvals = []
for gender, revenue in zip(genders, incomes):
    if gender == 'Male':
        # Traditionally, males are permitted
        approvals.append(1)
    else:
        # Solely females with excessive revenue are permitted
        approvals.append(1 if revenue > 80000 else 0)

train_df = pd.DataFrame({'Gender': genders, 'Revenue': incomes, 'Accepted': approvals})

# Changing classes to numbers for the machine studying mannequin
train_df['Gender_Code'] = train_df['Gender'].map({'Male': 1, 'Feminine': 0})

# 2. Coaching a Determination Tree classifier
mannequin = DecisionTreeClassifier(max_depth=3)
mannequin.match(train_df[['Gender_Code', 'Income']], train_df['Approved'])

The following step reveals Mimesis in motion. We’ll use this library to generate a small set of check topics utilizing the Generic class. This shall be executed by defining three base monetary profiles that include random UUIDs (universally distinctive identifiers) and a average revenue ranging between 40K and 70K. Discover that these profiles won’t have gender info integrated but:

from mimesis import Generic

generic = Generic('en')

# Producing 3 base monetary profiles
base_profiles = []
for _ in vary(3):
    profile = {
        'Applicant_ID': generic.cryptographic.uuid(),
        'Revenue': generic.random.randint(40000, 70000) # Reasonable revenue
    }
    base_profiles.append(profile)

For instance, the three newly created profiles could look one thing like:

[{'Applicant_ID': '1f1721e1-19af-4bd1-8488-6abf01404ef9', 'Income': 44815},
 {'Applicant_ID': '5c862597-7f55-43f4-9d6e-ac9cc0b9083e', 'Income': 47436},
 {'Applicant_ID': '3479d4cf-0d9b-4f06-9c43-1c3b7e787830', 'Income': 58194}]

Let’s end constructing our counterfactual set of examples, which constitutes the core of our auditing course of! For every of the three base profiles, we are going to create two cloned counterfactual cases: one being male and the opposite being feminine. For every pair of check clients, their utility ID and revenue shall be completely equivalent, so the one distinction would be the gender: any distinction in how our educated choice tree mannequin treats them will undoubtedly be proof of gender bias.

counterfactual_data = []

for profile in base_profiles:
    # Model A: Male Counterfactual
    counterfactual_data.append({
        'Applicant_ID': profile['Applicant_ID'], 
        'Gender': 'Male', 
        'Gender_Code': 1, 
        'Revenue': profile['Income']
    })
    
    # Model B: Feminine Counterfactual
    counterfactual_data.append({
        'Applicant_ID': profile['Applicant_ID'], 
        'Gender': 'Feminine', 
        'Gender_Code': 0, 
        'Revenue': profile['Income']
    })

audit_df = pd.DataFrame(counterfactual_data)

That is what the three pairs of consumers could appear like:

1f1721e1-19af-4bd1-8488-6abf01404ef9	Male	1	44815
1	1f1721e1-19af-4bd1-8488-6abf01404ef9	Feminine	0	44815
2	5c862597-7f55-43f4-9d6e-ac9cc0b9083e	Male	1	47436
3	5c862597-7f55-43f4-9d6e-ac9cc0b9083e	Feminine	0	47436
4	3479d4cf-0d9b-4f06-9c43-1c3b7e787830	Male	1	58194
5	3479d4cf-0d9b-4f06-9c43-1c3b7e787830	Feminine	0	58194

A key level to insist on right here: we have now simply used Mimesis to immediately construct completely matched “clones” of mortgage candidates with equivalent revenue however totally different genders. This underlines the library’s worth in offering complete statistical management, isolating a protected attribute.

Now it is time to probe the mannequin and see what it reveals.

# Asking the mannequin to foretell approval for our counterfactuals
audit_df['Predicted_Approval'] = mannequin.predict(audit_df[['Gender_Code', 'Income']])

# Formatting the output for readability (1 = Accepted, 0 = Denied)
audit_df['Predicted_Approval'] = audit_df['Predicted_Approval'].map({1: 'Accepted', 0: 'Denied'})

print("n--- Mannequin Audit Outcomes ---")
print(audit_df[['Applicant_ID', 'Gender', 'Income', 'Predicted_Approval']].sort_values('Applicant_ID'))

The choice-making outcomes yielded by our mannequin couldn’t be clearer:

--- Mannequin Audit Outcomes ---
                           Applicant_ID  Gender  Revenue Predicted_Approval
0  1f1721e1-19af-4bd1-8488-6abf01404ef9    Male   44815           Accepted
1  1f1721e1-19af-4bd1-8488-6abf01404ef9  Feminine   44815             Denied
4  3479d4cf-0d9b-4f06-9c43-1c3b7e787830    Male   58194           Accepted
5  3479d4cf-0d9b-4f06-9c43-1c3b7e787830  Feminine   58194             Denied
2  5c862597-7f55-43f4-9d6e-ac9cc0b9083e    Male   47436           Accepted
3  5c862597-7f55-43f4-9d6e-ac9cc0b9083e  Feminine   47436             Denied

Discover that for the very same Applicant_ID and Revenue, male clones are permitted for the mortgage. In the meantime, feminine clones with such average revenue are usually denied. The Mimesis functionalities we used primarily based on profiles helped us maintain all different variables fixed, thereby efficiently isolating and exposing the mannequin’s discriminatory decision-making.

# Wrapping Up

All through this hands-on article, we have now proven how Mimesis can be utilized to generate balanced, counterfactual knowledge examples — with out privateness or delicate knowledge constraints — that may assist audit a mannequin’s conduct and establish whether or not the mannequin is behaving in a biased method or not. Subsequent steps to take in case your mannequin is biased could embrace:

Augmenting your coaching knowledge with extra balanced profiles to right historic skewness or bias.
Relying on the mannequin sort, utilizing mannequin re-weighting methods.
Using open-source toolkits for equity — as an illustration, AI Equity 360 — that are useful for bias mitigation in machine studying pipelines.

Iván Palomares Carrascosa is a frontrunner, author, speaker, and adviser in AI, machine studying, deep studying & LLMs. He trains and guides others in harnessing AI in the true world.

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