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🧠 Vanguard A/B Test Analysis – Funnel Optimization

🧩 Business Context

Vanguard, a global investment management leader, recently launched a digital redesign of its customer onboarding experience. To assess the true impact of this redesign, the company conducted an A/B test.
Users were randomly assigned to either the control group (original user journey) or the treatment group (newly redesigned flow). The objective:
Measure if the redesign leads to a higher funnel completion rate, fewer drop-offs, and better user experience.

Note

This project simulates a real-life product experiment. It was developed during a Data Analysis Bootcamp to replicate decision-making scenarios based on real A/B testing data.


📦 Dataset Overview

The dataset consists of user navigation events throughout the onboarding funnel:

  • user_id: Unique identifier per user.
  • group: A/B group label – control or treatment.
  • step: Funnel step (e.g., step_1, step_2, ..., confirm).
  • timestamp: Timestamp of the event.
  • Derived fields (created in preprocessing):
    • time_diff: Time difference between steps.
    • final_step: Last recorded step per user.
    • error_flags: Indicators for anomalies.

🧹 Data Cleaning & Wrangling

To ensure valid insights, we applied rigorous data preprocessing steps:

  • Chronologically sorted user steps.
  • Removed sessions with:
    • Repeated steps (e.g., multiple step_2s).
    • Backward jumps (e.g., step_3 to step_1).
    • Zero-second step transitions.
  • Labeled sessions that did not end in confirm as abandonments.
  • Engineered features for:
    • Time spent per step.
    • Funnel depth reached.
    • Navigation consistency.

These cleaning rules were based on domain assumptions. In a production setting, more session metadata and UX feedback would further guide this logic.


📊 Exploratory Data Analysis

The EDA compared control vs. treatment groups on multiple dimensions:

  • Completion Rate – % of users reaching the confirm step.
  • Drop-off Points – Common exit steps.
  • Navigation Errors – Frequency of repeated or reversed steps.
  • Time Metrics – Total and per-step time comparisons.

Key visualizations:

  • Funnel diagrams by group
  • Step-wise conversion rates
  • Session length distributions

🧪 Hypothesis Testing

We ran statistical tests to validate whether differences observed were statistically significant:

  • Z-test for proportions (completion rate comparison).
  • T-test / Mann-Whitney U test (time differences).
  • Chi-squared test (distribution of final steps and errors).
  • Sanity checks for group balance and random assignment.

Assumptions tested:

  • Normality (Shapiro-Wilk, histograms).
  • Equal variances (Levene's test).

Statistical significance ≠ business impact. All insights were contextualized with user experience and operational considerations.


📈 Key Insights
  • Higher completion rate in the treatment group (statistically significant).
  • 🔄 Fewer navigation errors post-redesign, especially backward transitions.
  • ⏱️ Time efficiency slightly improved but not statistically conclusive.
  • 🧩 Users followed a more linear path in the redesigned flow.

🧭 Recommendations
  • Roll out the redesign to the broader user base.
  • 📊 Monitor funnel metrics continuously to detect regressions.
  • 🔬 Run additional segmented tests (e.g., new vs. returning users).
  • 🧠 Gather qualitative UX insights (e.g., via surveys, heatmaps).
  • ⚙️ Improve experiment design with longer run times and controlled traffic splits.

🧑‍🏫 Educational Context

This analysis was developed as part of a Data Analytics Bootcamp.
It reflects industry-standard approaches to experimentation, data cleaning, and interpretation of A/B tests within digital products.


🚀 Streamlit App

As part of this project, we built an interactive web application using Streamlit to visualize key insights from the A/B test, including:

  • Funnel completion rate comparisons
  • Drop-off analysis by step
  • KPIs and error rates
  • Demographic exploration

You can explore the full dashboard here:
👉 Launch the Streamlit App

ℹ️ Best viewed on desktop for full dashboard interaction.


👥 Authors

Rocío

Xavi


Python Jupyter Tableau Streamlit Status

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