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Bayesian Machine Learning in Python: A/B Testing (Udemy.com)

Data Science, Machine Learning, and Data Analytics Techniques for Marketing, Digital Media, Online Advertising, and More

Created by: Lazy Programmer Inc.

Last updated August 2026

Our take

Based on the ratings of 8,053 students, a sample of their written reviews and the syllabus, as the course stood in August 2026. No course pays to be reviewed.

This is a 10.4-hour course that uses A/B testing as the vehicle for Bayesian thinking. It opens with a probability review, moves into traditional t-tests and frequentist testing, then spends its biggest block, 25 lectures, on Bayesian A/B testing. Everything is coded in Python with the Numpy stack, mostly on simulated data. The prerequisites are real, and one reviewer found it a bit easy on both the stats and Python side.

Praise centers on clear explanations of hard material. One reviewer liked that the frequentist walkthroughs explain enough theory to avoid blind library calls, and ranked it above the A/B courses from Dataquest and Datacamp. Others say Lazy Programmer Inc. keeps a dense topic interesting. The complaints are consistent too. Some find the lectures dry and equation-heavy. Others say the Bayesian part is thinner than the runtime suggests, with off-topic videos and plugs for other courses. A few wanted more intuition for beta distributions and a full case study. The code comes as .py files, not notebooks.

Rated 4.7 by about 8,000 students, with 47,600 enrolled and a refresh in August 2026, so it's current. More than two hours of the runtime is appendix on setup, Python help and study habits, which leaves about eight hours of core material. It suits someone with a stats background who wants to see bandits and Bayesian updating built step by step. For fast intuition, one reviewer pointed to Statistical Rethinking instead.

Best forData folks with probability and Numpy basics who want bandits and Bayesian A/B testing built by hand.
Skip it ifYou want quick intuition, polished notebooks, or a deep Bayesian course that goes well beyond A/B testing.

Pros

  • Builds epsilon-greedy, UCB1 and Bayesian A/B methods by hand in Python, not library calls
  • Probability review and frequentist walkthroughs praised as clear and well paced
  • Refreshed in August 2026 and rated 4.7 across roughly 8,000 ratings
  • Compares traditional and Bayesian testing side by side in a single course

Cons

  • Over two hours of appendix on setup and study tips pads the 10.4-hour runtime
  • Bayesian core feels thin to some, with little intuition for beta distributions
  • Code is in .py files rather than notebooks, and there is no full case study
The walkthroughs of frequentist statistics are very good. They explain enough of the underlying theory so that you don't feel like you're blindly plugging inputs into pre-built functions from libraries.
Justin J, a student

Listed as All Levels, but it assumes probability and Numpy skills. True beginners will struggle.

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What you will learn

  • Use adaptive algorithms to improve A/B testing performance
  • Understand the difference between Bayesian and frequentist statistics
  • Apply Bayesian methods to A/B testing

Course content

12 sections · 80 lectures · 10 hours of video 1 quiz, 1 practice test

  1. 1Introduction and Outline 1 free preview3 lectures · 19 min
  2. 2The High-Level Picture2 lectures · 18 min
  3. 3Bayes Rule and Probability Review14 lectures · 1.6 hours
  4. 4Traditional A/B Testing17 lectures · 2.1 hours
  5. 5Bayesian A/B Testing 1 free preview25 lectures · 2.9 hours
  6. 6Bayesian A/B Testing Extension3 lectures · 19 min
  7. 7Practice Makes Perfect3 lectures · 1 quiz · 18 min
  8. 8Appendix / FAQ Intro1 lecture · 4 min
  9. 9Setting Up Your Environment (FAQ by Student Request)3 lectures · 42 min
  10. 10Extra Help With Python Coding for Beginners (FAQ by Student Request)4 lectures · 42 min

Who it is for

The instructor says it suits

  • Students and professionals with a technical background who want to learn Bayesian machine learning techniques to apply to their data science work

What you need before you start

  • Probability (joint, marginal, conditional distributions, continuous and discrete random variables, PDF, PMF, CDF)
  • Python coding with the Numpy stack

How it compares

Against the other 155 rated Udemy courses in Machine Learning on CourseDuck:

  • Rating4.7 out of 5higher than 93% of them
  • Reviews8,053#13 of 156 by number of reviews
  • Length10.4 hourslonger than 63% of them
  • Last updatedAugust 2026more recently than 90% of them

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Quality Score

Content Quality
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Video Quality
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Qualified Instructor
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Course Depth & Coverage
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Overall Score : 94 / 100

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Course Description

This course is all about A/B testing.

A/B testing is used everywhere. Marketing, retail, newsfeeds, online advertising, and more.

A/B testing is all about comparing things.

If you’re a data scientist, and you want to tell the rest of the company, “logo A is better than logo B”, well you can’t just say that without proving it using numbers and statistics.

Traditional A/B testing has been around for a long time, and it’s full of approximations and confusing definitions.

In this course, while we will do traditional A/B testing in order to appreciate its complexity, what we will eventually get to is the Bayesian machine learning way of doing things.

First, we’ll see if we can improve on traditional A/B testing with adaptive methods. These all help you solve the explore-exploit dilemma.

You’ll learn about the epsilon-greedy algorithm, which you may have heard about in the context of reinforcement learning.

We’ll improve upon the epsilon-greedy algorithm with a similar algorithm called UCB1.

Finally, we’ll improve on both of those by using a fully Bayesian approach.

Why is the Bayesian method interesting to us in machine learning?

It’s an entirely different way of thinking about probability.

It’s a paradigm shift.

You’ll probably need to come back to this course several times before it fully sinks in.

It’s also powerful, and many machine learning experts often make statements about how they “subscribe to the Bayesian school of thought”.

In sum - it’s going to give us a lot of powerful new tools that we can use in machine learning.

The things you’ll learn in this course are not only applicable to A/B testing, but rather, we’re using A/B testing as a concrete example of how Bayesian techniques can be applied.

You’ll learn these fundamental tools of the Bayesian method - through the example of A/B testing - and then you’ll be able to carry those Bayesian techniques to more advanced machine learning models in the future.

See you in class!

"If you can't implement it, you don't understand it"

  • Or as the great physicist Richard Feynman said: "What I cannot create, I do not understand".

  • My courses are the ONLY courses where you will learn how to implement machine learning algorithms from scratch

  • Other courses will teach you how to plug in your data into a library, but do you really need help with 3 lines of code?

  • After doing the same thing with 10 datasets, you realize you didn't learn 10 things. You learned 1 thing, and just repeated the same 3 lines of code 10 times...


Suggested Prerequisites:

  • Probability (joint, marginal, conditional distributions, continuous and discrete random variables, PDF, PMF, CDF)

  • Python coding: if/else, loops, lists, dicts, sets

  • Numpy, Scipy, Matplotlib


WHAT ORDER SHOULD I TAKE YOUR COURSES IN?:

  • Check out the lecture "Machine Learning and AI Prerequisite Roadmap" (available in the FAQ of any of my courses, including the free Numpy course)


UNIQUE FEATURES

  • Every line of code explained in detail - email me any time if you disagree

  • No wasted time "typing" on the keyboard like other courses - let's be honest, nobody can really write code worth learning about in just 20 minutes from scratch

  • Not afraid of university-level math - get important details about algorithms that other courses leave out

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Instructor Details

Lazy Programmer Inc.

The Lazy Programmer is a seasoned online educator with an unwavering passion for sharing knowledge. With over 10 years of experience, he has revolutionized the field of data science and machine learning by captivating audiences worldwide through his comprehensive courses and tutorials.


Equipped with a multidisciplinary background, the Lazy Programmer holds a remarkable duo of master's degrees. His first foray into academia led him to pursue computer engineering, with a specialized focus on machine learning and pattern recognition. Undeterred by boundaries, he then ventured into the realm of statistics, exploring its applications in financial engineering.


Recognized as a trailblazer in his field, the Lazy Programmer quickly embraced the power of deep learning when it was still in its infancy. As one of the pioneers, he fearlessly embarked on instructing one of the first-ever online courses on deep learning, catapulting him to the forefront of the industry.


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Reviews

4.7

8,053 ratings on Udemy

Select a bar to show only those reviews.Select the bar again to show every rating.

By Mzingisi Magadlela on 11/6/2025

Job well done! This course is a fantastic resource for anyone looking to deepen their understanding of Bayesian methods in machine learning. Whether a beginner or someone with a statistical background, you will find this course enriching and valuable. It has equipped me with the tools to approach machine learning problems with a Bayesian mindset, and I feel confident applying these new skills in my projects.

By Justin J on 10/1/2024

The probability review has clear explanations. Since it's review, there's no time wasted on needlessly detailed explanations of concepts we should already know as prereqs. Served as a great refresher. The walkthroughs of frequentist statistics are very good. They explain enough of the underlying theory so that you don't feel like you're blindly plugging inputs into pre-built functions from libraries. Thus far, this course has been far better than the A/B testing courses from Dataquest and Datacamp.

By Anonymized User on 1/4/2023

Having taken many online courses in different web-learning platforms, I thought was better than what I was expecting from this course. The way you taught quite complex concepts was really straightforward and easy to follow. I think you could reconsider the name of the course as I think it was a bit misleading, as you covered so much material that with a bit more content I think you could make a whole program out of this with different chapters for different statistics/ML topics. Great work! I look forward in checking your other courses.

By Mario Luis on 4/14/2022

Very hard course but very well instructed. I have got some certificates already from other courses from Lazy Programmer and they are all taken very seriously by the instructor, it is like a real university classroom course, exercises are hard, you have to rewatch a lot sometimes to understand the content clearly but then you get it and you can do the exercises. You must dedicate enough time on it... In the end you feel that you understand the subject and it will naturally pop up on your head when you think of an application where it may be useful to solve the problem...

By Inchan Hwang on 1/24/2022

I have been through more than half of the course materials. By now, I can confidently tell you that Lazy programmer would not let you down for his courses. It is one of few courses over Udemy that I can recommend anyone to watch. I am sure you will learn something out of his course materials. By the way, Does Lazy programmer offer other courses on Bayesian statistics? at least somewhat related with Bayesian statistics?

By Anonymized User on 6/17/2021

In bandit design lecture used many-to-many relationship but it is clearly one-to-one. In bandit summary lecture properties of online learning are secondary to online learning itself and can be changed in online learning. Also in data that can be real-world is used in course, for example in the adaptive ad server exercise lecture. If the author is don't want to search data - ok, but tell truth. The last one issue impacted this rate the most.

By lu yi wong on 2/16/2021

teacher is an expert at his field. maybe less in teaching. unique in-depth content. students should have had some experience with programming classes and objects, as well as dunder methods and list comprehensions code can be more readable with better naming instead of alphabets. waste time reading it. also should include printing python objects (i googled for a solution) as console.log is essential for coding to view under the hood.

By Steven Miller on 1/23/2021

This is truly an amazing class. These courses are just what I am looking for. You are giving us the mathematics behind the techniques and then giving us a chance to code it and check the code. Really great stuff. I have the remainder of your data science courses and look forward to taking them. Nice JOB!

By Vladimir Avanesyan on 11/28/2020

In my opinion the course is good - it is well organized, each section starts with detailed explanation of theory followed by numerous code examples and exercises. The example code is compact, self explanatory with lots of comments, requires little experiense in Python. The instructor is professional in teaching ML. I had no difficulty to follow up his lectures with my intermediate English. The course still wants more in-depth theory and exercises on Bayes A/B testing, a final project would be a plus. Also it seems not very efficient to include sections 8,9,10 (2h+ video) in each Lazy course - one can find all these topics in the "Deep Learning Prerequisites" :).

By Yasamin Khorramzadeh on 7/3/2017

This was the most efficient and concise online course I have ever taken! The instructor is on to the point and avoids unnecessary explanation (yet suggesting references for the curious to explore further. ) He repeats and emphasizes the takeaway points of each lecture just the right number of times! I'm no set off to take some of his other courses.

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