Tu vas découvrir les probabilités conditionnelles, un concept super... Show more
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Knowunity AI
Subjects
Triangle Congruence and Similarity Theorems
Triangle Properties and Classification
Linear Equations and Graphs
Geometric Angle Relationships
Trigonometric Functions and Identities
Equation Solving Techniques
Circle Geometry Fundamentals
Division Operations and Methods
Basic Differentiation Rules
Exponent and Logarithm Properties
Show all topics
Human Organ Systems
Reproductive Cell Cycles
Biological Sciences Subdisciplines
Cellular Energy Metabolism
Autotrophic Energy Processes
Inheritance Patterns and Principles
Biomolecular Structure and Organization
Cell Cycle and Division Mechanics
Cellular Organization and Development
Biological Structural Organization
Show all topics
Chemical Sciences and Applications
Atomic Structure and Composition
Molecular Electron Structure Representation
Atomic Electron Behavior
Matter Properties and Water
Mole Concept and Calculations
Gas Laws and Behavior
Periodic Table Organization
Chemical Thermodynamics Fundamentals
Chemical Bond Types and Properties
Show all topics
European Renaissance and Enlightenment
European Cultural Movements 800-1920
American Revolution Era 1763-1797
American Civil War 1861-1865
Global Imperial Systems
Mongol and Chinese Dynasties
U.S. Presidents and World Leaders
Historical Sources and Documentation
World Wars Era and Impact
World Religious Systems
Show all topics
Classic and Contemporary Novels
Literary Character Analysis
Rhetorical Theory and Practice
Classic Literary Narratives
Reading Analysis and Interpretation
Narrative Structure and Techniques
English Language Components
Influential English-Language Authors
Basic Sentence Structure
Narrative Voice and Perspective
Show all topics
32
•
Updated Mar 19, 2026
•
Tu vas découvrir les probabilités conditionnelles, un concept super... Show more











Imagine que tu veuilles savoir si un composant électronique est vraiment cassé quand un test le dit défectueux. C'est exactement ce que permettent les probabilités conditionnelles !
Dans ce premier exercice, on découvre qu'une entreprise fabrique des composants dont seulement 2% sont défectueux. Elle utilise un test fiable à 95% pour détecter les défauts et à 98% pour confirmer que les bons composants fonctionnent bien.
Le plus fascinant ? Même avec un test très fiable, quand il dit qu'un composant est défectueux, il n'y a que 49% de chances qu'il le soit vraiment ! Ça peut sembler bizarre, mais c'est à cause du petit nombre de composants défectueux au départ.
À retenir : La formule de Bayes permet de calculer la probabilité qu'un événement soit vrai quand on connaît le résultat d'un test.

Les arbres pondérés sont comme des cartes routières pour les probabilités ! Dans l'exercice sur les transports, 60% des habitants utilisent les transports en commun et 40% leur voiture.
Voici ce qui est intéressant : parmi ceux qui prennent les transports en commun, seulement 10% arrivent en retard, contre 20% pour ceux en voiture. Au final, 14% des habitants arrivent en retard au travail.
Si quelqu'un arrive en retard, il y a environ 43% de chances qu'il ait pris les transports en commun. Ces événements ne sont pas indépendants car le moyen de transport influence les retards.
Astuce pratique : Pour vérifier l'indépendance, compare P(A∩B) avec P(A)×P(B). Si c'est différent, les événements sont liés !

Quand tu tires des boules d'une urne sans les remettre, les probabilités changent à chaque tirage ! Avec 6 boules rouges et 4 noires, tu as 60% de chances de tirer une rouge au début.
Mais si la première est rouge, il ne reste que 5 rouges sur 9 boules, donc 5/9 de chances pour la deuxième. La probabilité d'avoir deux rouges consécutives devient 1/3.
Le problème devient encore plus cool avec deux urnes différentes ! En utilisant la formule de Bayes, on peut déterminer de quelle urne vient une boule rouge. C'est comme être détective avec les maths !
Le truc en plus : Dans les tirages sans remise, chaque tirage modifie la composition de l'urne pour les tirages suivants.







Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
App Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Tu vas découvrir les probabilités conditionnelles, un concept super utile qui permet de calculer des chances quand tu connais déjà certaines informations ! On va voir comment résoudre des problèmes avec des tests médicaux, des transports et des tirages... Show more

Access to all documents
Improve your grades
Join milions of students
Imagine que tu veuilles savoir si un composant électronique est vraiment cassé quand un test le dit défectueux. C'est exactement ce que permettent les probabilités conditionnelles !
Dans ce premier exercice, on découvre qu'une entreprise fabrique des composants dont seulement 2% sont défectueux. Elle utilise un test fiable à 95% pour détecter les défauts et à 98% pour confirmer que les bons composants fonctionnent bien.
Le plus fascinant ? Même avec un test très fiable, quand il dit qu'un composant est défectueux, il n'y a que 49% de chances qu'il le soit vraiment ! Ça peut sembler bizarre, mais c'est à cause du petit nombre de composants défectueux au départ.
À retenir : La formule de Bayes permet de calculer la probabilité qu'un événement soit vrai quand on connaît le résultat d'un test.

Access to all documents
Improve your grades
Join milions of students
Les arbres pondérés sont comme des cartes routières pour les probabilités ! Dans l'exercice sur les transports, 60% des habitants utilisent les transports en commun et 40% leur voiture.
Voici ce qui est intéressant : parmi ceux qui prennent les transports en commun, seulement 10% arrivent en retard, contre 20% pour ceux en voiture. Au final, 14% des habitants arrivent en retard au travail.
Si quelqu'un arrive en retard, il y a environ 43% de chances qu'il ait pris les transports en commun. Ces événements ne sont pas indépendants car le moyen de transport influence les retards.
Astuce pratique : Pour vérifier l'indépendance, compare P(A∩B) avec P(A)×P(B). Si c'est différent, les événements sont liés !

Access to all documents
Improve your grades
Join milions of students
Quand tu tires des boules d'une urne sans les remettre, les probabilités changent à chaque tirage ! Avec 6 boules rouges et 4 noires, tu as 60% de chances de tirer une rouge au début.
Mais si la première est rouge, il ne reste que 5 rouges sur 9 boules, donc 5/9 de chances pour la deuxième. La probabilité d'avoir deux rouges consécutives devient 1/3.
Le problème devient encore plus cool avec deux urnes différentes ! En utilisant la formule de Bayes, on peut déterminer de quelle urne vient une boule rouge. C'est comme être détective avec les maths !
Le truc en plus : Dans les tirages sans remise, chaque tirage modifie la composition de l'urne pour les tirages suivants.

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students

Access to all documents
Improve your grades
Join milions of students
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
App Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user