Allen Downey
@allendowney.bsky.social
Former professor at Olin College, principal data scientist at PyMC Labs, author of Think Python, and Probably Overthinking It -- blog and book -- and stark raving Bayesian.
The newest chapter of Think Linear Algebra is up now!
It is about least squares regression, QR decomposition, and orthogonality:
allendowney.github.io/ThinkLinearA...
It is about least squares regression, QR decomposition, and orthogonality:
allendowney.github.io/ThinkLinearA...
October 29, 2025 at 2:30 PM
The newest chapter of Think Linear Algebra is up now!
It is about least squares regression, QR decomposition, and orthogonality:
allendowney.github.io/ThinkLinearA...
It is about least squares regression, QR decomposition, and orthogonality:
allendowney.github.io/ThinkLinearA...
I just posted a new chapter of Think Linear Algebra.
It's about projection, rejection, rotation, and pool!
allendowney.github.io/ThinkLinearA...
It's about projection, rejection, rotation, and pool!
allendowney.github.io/ThinkLinearA...
October 19, 2025 at 5:54 PM
I just posted a new chapter of Think Linear Algebra.
It's about projection, rejection, rotation, and pool!
allendowney.github.io/ThinkLinearA...
It's about projection, rejection, rotation, and pool!
allendowney.github.io/ThinkLinearA...
Sometimes we can use Bayesian methods to infer the effect of selection bias and produce an unbiased estimate.
Here's an example that uses PyMC to solve a classic probability puzzle (the image shows what I think is the original version).
www.allendowney.com/blog/2025/09...
Here's an example that uses PyMC to solve a classic probability puzzle (the image shows what I think is the original version).
www.allendowney.com/blog/2025/09...
September 26, 2025 at 1:43 PM
Sometimes we can use Bayesian methods to infer the effect of selection bias and produce an unbiased estimate.
Here's an example that uses PyMC to solve a classic probability puzzle (the image shows what I think is the original version).
www.allendowney.com/blog/2025/09...
Here's an example that uses PyMC to solve a classic probability puzzle (the image shows what I think is the original version).
www.allendowney.com/blog/2025/09...
I have published five new chapters of Think Linear Algebra!
Read about the project here
allendowney.com/blog/2025/09...
Or jump straight to the book
allendowney.github.io/ThinkLinearA...
And now… Asteroids!
Read about the project here
allendowney.com/blog/2025/09...
Or jump straight to the book
allendowney.github.io/ThinkLinearA...
And now… Asteroids!
September 22, 2025 at 2:41 PM
I have published five new chapters of Think Linear Algebra!
Read about the project here
allendowney.com/blog/2025/09...
Or jump straight to the book
allendowney.github.io/ThinkLinearA...
And now… Asteroids!
Read about the project here
allendowney.com/blog/2025/09...
Or jump straight to the book
allendowney.github.io/ThinkLinearA...
And now… Asteroids!
Between 2021 and 2024, marijuana was legalized in eight states totaling 18% of the US population. During this time, adult use increased and youth use was unchanged.
Data from NSDUH 2024.
Data from NSDUH 2024.
August 13, 2025 at 5:16 PM
Between 2021 and 2024, marijuana was legalized in eight states totaling 18% of the US population. During this time, adult use increased and youth use was unchanged.
Data from NSDUH 2024.
Data from NSDUH 2024.
ChatGPT and I think that "AI tools are shifting the boundary of what’s viable, and that’s likely to increase the net demand for software development, not decrease it."
More Viable Projects = More Things to Build
chatgpt.com/share/686c2e...
More Viable Projects = More Things to Build
chatgpt.com/share/686c2e...
July 7, 2025 at 8:29 PM
ChatGPT and I think that "AI tools are shifting the boundary of what’s viable, and that’s likely to increase the net demand for software development, not decrease it."
More Viable Projects = More Things to Build
chatgpt.com/share/686c2e...
More Viable Projects = More Things to Build
chatgpt.com/share/686c2e...
My Think Stats hard copy has arrived!
Here's what's new in the third edition:
allendowney.github.io/ThinkStats/c...
Here's what's new in the third edition:
allendowney.github.io/ThinkStats/c...
April 28, 2025 at 12:38 PM
My Think Stats hard copy has arrived!
Here's what's new in the third edition:
allendowney.github.io/ThinkStats/c...
Here's what's new in the third edition:
allendowney.github.io/ThinkStats/c...
Think Stats 3e is on its way to the printer!
(And available to pre-order)
Here's the new cover, with a suspicious-looking archerfish.
Blog post with the details: www.allendowney.com/blog/2025/04...
(And available to pre-order)
Here's the new cover, with a suspicious-looking archerfish.
Blog post with the details: www.allendowney.com/blog/2025/04...
April 7, 2025 at 1:46 PM
Think Stats 3e is on its way to the printer!
(And available to pre-order)
Here's the new cover, with a suspicious-looking archerfish.
Blog post with the details: www.allendowney.com/blog/2025/04...
(And available to pre-order)
Here's the new cover, with a suspicious-looking archerfish.
Blog post with the details: www.allendowney.com/blog/2025/04...
Here's one for comparison
February 15, 2025 at 2:13 PM
Here's one for comparison
New bird on my feeder this morning. I think it's a ruby-crowned kinglet, but maybe @jerthorp.bsky.social can confirm or deny.
February 15, 2025 at 2:11 PM
New bird on my feeder this morning. I think it's a ruby-crowned kinglet, but maybe @jerthorp.bsky.social can confirm or deny.
New German translation of Think Python 3rd edition!
January 22, 2025 at 4:24 PM
New German translation of Think Python 3rd edition!
Confidence in the press has been declining since the 1970s.
The trend might have reversed among liberals, so polarization has increased.
open.substack.com/pub/allendow...
The trend might have reversed among liberals, so polarization has increased.
open.substack.com/pub/allendow...
January 12, 2025 at 3:22 PM
Confidence in the press has been declining since the 1970s.
The trend might have reversed among liberals, so polarization has increased.
open.substack.com/pub/allendow...
The trend might have reversed among liberals, so polarization has increased.
open.substack.com/pub/allendow...
Recently I posted NSFG data showing marriage patterns for young women in the U.S. compared to previous generations. The percentage of women married before age 24 has dropped to about 10%.
Now here's the same analysis for young men. The pattern is similar -- very few young men are getting married.
Now here's the same analysis for young men. The pattern is similar -- very few young men are getting married.
January 4, 2025 at 2:50 PM
Recently I posted NSFG data showing marriage patterns for young women in the U.S. compared to previous generations. The percentage of women married before age 24 has dropped to about 10%.
Now here's the same analysis for young men. The pattern is similar -- very few young men are getting married.
Now here's the same analysis for young men. The pattern is similar -- very few young men are getting married.
Young Americans are marrying later, and it looks like more of them will remain unmarried
Updated with new data from the National Survey of Family Growth
Updated with new data from the National Survey of Family Growth
December 11, 2024 at 7:16 PM
Young Americans are marrying later, and it looks like more of them will remain unmarried
Updated with new data from the National Survey of Family Growth
Updated with new data from the National Survey of Family Growth
How does income vary with education and age?
Another excerpt from Elements of Data Science, Multiple Regression with StatModels
allendowney.substack.com/p/multiple-r...
Another excerpt from Elements of Data Science, Multiple Regression with StatModels
allendowney.substack.com/p/multiple-r...
December 9, 2024 at 2:24 PM
How does income vary with education and age?
Another excerpt from Elements of Data Science, Multiple Regression with StatModels
allendowney.substack.com/p/multiple-r...
Another excerpt from Elements of Data Science, Multiple Regression with StatModels
allendowney.substack.com/p/multiple-r...
Recently I heard the word chartist for the first time in 57 years.
Then within the same day, I heard it again.
What are the chances? I used Bayes's theorem and a large corpus of English words to find out.
www.allendowney.com/blog/2024/11...
Then within the same day, I heard it again.
What are the chances? I used Bayes's theorem and a large corpus of English words to find out.
www.allendowney.com/blog/2024/11...
November 19, 2024 at 4:14 PM
Recently I heard the word chartist for the first time in 57 years.
Then within the same day, I heard it again.
What are the chances? I used Bayes's theorem and a large corpus of English words to find out.
www.allendowney.com/blog/2024/11...
Then within the same day, I heard it again.
What are the chances? I used Bayes's theorem and a large corpus of English words to find out.
www.allendowney.com/blog/2024/11...
If you cherry pick gender differences in political beliefs, you can generate headlines. But if you look systematically, differences on most issues are small, and it doesn't seem like they are growing.
New collaboration with AIBM: allendowney.substack.com/cp/151030453
New collaboration with AIBM: allendowney.substack.com/cp/151030453
November 1, 2024 at 2:58 PM
If you cherry pick gender differences in political beliefs, you can generate headlines. But if you look systematically, differences on most issues are small, and it doesn't seem like they are growing.
New collaboration with AIBM: allendowney.substack.com/cp/151030453
New collaboration with AIBM: allendowney.substack.com/cp/151030453
Yesterday I presented a webinar about solving The Red Line Problem with PyMC. You can watch the video and get the slides here:
www.allendowney.com/blog/2024/07...
Come for the Bayesian statistics -- stay for the Banana of Ignorance!
www.allendowney.com/blog/2024/07...
Come for the Bayesian statistics -- stay for the Banana of Ignorance!
July 25, 2024 at 3:58 PM
Yesterday I presented a webinar about solving The Red Line Problem with PyMC. You can watch the video and get the slides here:
www.allendowney.com/blog/2024/07...
Come for the Bayesian statistics -- stay for the Banana of Ignorance!
www.allendowney.com/blog/2024/07...
Come for the Bayesian statistics -- stay for the Banana of Ignorance!
I had the pleasure of collaborating with Richard Reeves on this article related to trends in support for gender equality.
ofboysandmen.substack.com/p/no-young-m...
It's mostly good news: on principles of gender equality we see consistent progress and little/no evidence of divergence or backlash.
ofboysandmen.substack.com/p/no-young-m...
It's mostly good news: on principles of gender equality we see consistent progress and little/no evidence of divergence or backlash.
July 24, 2024 at 5:56 PM
I had the pleasure of collaborating with Richard Reeves on this article related to trends in support for gender equality.
ofboysandmen.substack.com/p/no-young-m...
It's mostly good news: on principles of gender equality we see consistent progress and little/no evidence of divergence or backlash.
ofboysandmen.substack.com/p/no-young-m...
It's mostly good news: on principles of gender equality we see consistent progress and little/no evidence of divergence or backlash.
Until July 31, Elements of Data Science is available for 20% off, only from Lulu.com
www.allendowney.com/blog/2024/07...
By self publishing, I can print full-color interior at a reasonable cover cost. Here's an example showing color code highlighting and data visualization.
www.allendowney.com/blog/2024/07...
By self publishing, I can print full-color interior at a reasonable cover cost. Here's an example showing color code highlighting and data visualization.
July 23, 2024 at 3:20 PM
Until July 31, Elements of Data Science is available for 20% off, only from Lulu.com
www.allendowney.com/blog/2024/07...
By self publishing, I can print full-color interior at a reasonable cover cost. Here's an example showing color code highlighting and data visualization.
www.allendowney.com/blog/2024/07...
By self publishing, I can print full-color interior at a reasonable cover cost. Here's an example showing color code highlighting and data visualization.
What is the difference between probability density and likelihood?
It's complicated because it's not really a "what's the difference" question. But here's my best answer:
www.allendowney.com/blog/2024/07...
It's complicated because it's not really a "what's the difference" question. But here's my best answer:
www.allendowney.com/blog/2024/07...
July 13, 2024 at 11:50 AM
What is the difference between probability density and likelihood?
It's complicated because it's not really a "what's the difference" question. But here's my best answer:
www.allendowney.com/blog/2024/07...
It's complicated because it's not really a "what's the difference" question. But here's my best answer:
www.allendowney.com/blog/2024/07...
Similarly with attendance at religious services, the gender gap has closed and possibly reversed.
June 30, 2024 at 12:23 PM
Similarly with attendance at religious services, the gender gap has closed and possibly reversed.
In the HERI Freshman Survey, women have been more religious than men for a long time. Not any more.
open.substack.com/pub/allendow...
open.substack.com/pub/allendow...
June 29, 2024 at 12:29 AM
In the HERI Freshman Survey, women have been more religious than men for a long time. Not any more.
open.substack.com/pub/allendow...
open.substack.com/pub/allendow...
This plum-headed parakeet is here to tell you that the third edition of Think Python is shipping now.
greenteapress.com/wp/think-pyt...
What's new? Jupyter notebooks, LLMs, more exercises, more testing, regular expressions, and turtles!
greenteapress.com/wp/think-pyt...
What's new? Jupyter notebooks, LLMs, more exercises, more testing, regular expressions, and turtles!
June 12, 2024 at 6:27 PM
This plum-headed parakeet is here to tell you that the third edition of Think Python is shipping now.
greenteapress.com/wp/think-pyt...
What's new? Jupyter notebooks, LLMs, more exercises, more testing, regular expressions, and turtles!
greenteapress.com/wp/think-pyt...
What's new? Jupyter notebooks, LLMs, more exercises, more testing, regular expressions, and turtles!
On a recent run with a Spanish friend, we wondered whether the population of Spain would be shrinking if there were no net immigration.
The answer is in this new blog post: www.allendowney.com/blog/2024/06...
The answer is in this new blog post: www.allendowney.com/blog/2024/06...
June 6, 2024 at 6:13 PM
On a recent run with a Spanish friend, we wondered whether the population of Spain would be shrinking if there were no net immigration.
The answer is in this new blog post: www.allendowney.com/blog/2024/06...
The answer is in this new blog post: www.allendowney.com/blog/2024/06...