How do you interpret a p-value?

What is a p-value and why is it so special if it’s less than 0.05? This video describes how scientists use p-values to decide if the difference between two data sets is real, or just due to random chance. Bonus: learn about cool research about how the bacteria in your gut might affect how much you weigh!
0:00 Introduction
0:18 Example from research: Mouse microbiome and obesity
1:10 Are the data sets really different?
2:23 What p-values help us do
3:13 Null Hypothesis and Alternative Hypothesis
3:37 Warning: Null & Alternative Hypotheses do not equal Scientific Hypothesis
4:08 What is a p-value?
5:46 Why is p less than 0.05 so special?
8:47 Does the microbiome of obese mice contribute to obesity?
The research study about the obesity and the microbiome in mice is:
P. J. Turnbaugh, et al., An obesity-associated gut microbiome with increased capacity for energy harvest. Nature 444, 1027-1031 (2006). doi.org/10.1038/nature05414
Scientific Consultation by Malcolm Campbell
Cartoon Illustrations by Michelle Lotker
p-value examples that pop up in the first 10 seconds are from these papers:
X. Ding, Z. Yang, Y. Han, H. Yu, Fatty Acid Oxidation Changes and the Correlation with Oxidative Stress in Different Preeclampsia-Like Mouse Models. PLOS ONE 9, e109554 (2014).
M. P. Mullen, J. P. Hanrahan, Direct Evidence on the Contribution of a Missense Mutation in GDF9 to Variation in Ovulation Rate of Finnsheep. PLOS ONE 9, e95251 (2014).
N. P. Ward, A. M. Poff, A. P. Koutnik, D. P. D’Agostino, Complex I inhibition augments dichloroacetate cytotoxicity through enhancing oxidative stress in VM-M3 glioblastoma cells. PLOS ONE 12, e0180061 (2017).
This video is copyright Jayme Dyer, published under the Creative Commons CC-BY SA 4.0 license.
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[@bowtiebiology8865]

I loved the splash screen at 3:40. Conflating the two different meanings of hypothesis is one of my pet peeves and something that I try to hit hard with my intro to bio students.

[@YouTooBio]

YES! This is why being a teacher makes my SciComm better - I wrote the script for this video in the summer of 2020, then I taught p-values to my Intro Bio students in the fall (20) and spring semesters (21) and both semesters, students conflated the null/alt. hypothesis with the scientific hypothesis. So I added that part into the script! Glad it hits the same points you find you need to address in your classes.

[@AtTheBenchtop]

Loved the back and forth and the editing was 👌! Another great vid!

[@YouTooBio]

Thanks! This was definitely Editing 2.0 - a fun challenge!

[@avigreenberg8329]

Just discovered your channel. Such great content! Thank you!!

[@YouTooBio]

Thanks!!

[@MerabZukhbaia]

very well explained, thanks

[@ravishmahajan9314]

Awwwsome🤩🤩🤩
Got it after going through astronomical number of articles and videos.
Just on simple question. I mean assuming null hypothesis is true and getting extremely smaller p value is not by chance but what if it's by chance and by luck we got that p value and we rejected null? How to deal with that failed research????

[@YouTooBio]

It happens!! XKCD has a good comic about that: xkcd.com/882/
How do scientists deal with it? Replicates! Others validate the results! Never decide that a conclusion is true based on a single experiment. "Scientific facts" are supported by lots and lots of experiments that generally agree with each other, knowing that sometimes by random chance we'll get data that don't support the "true" conclusion.