Stanford CS109 I Conditional Probability and Bayes I 2022 I Lecture 4

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  • เผยแพร่เมื่อ 29 ธ.ค. 2024

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  • @prithvib8662
    @prithvib8662 ปีที่แล้ว +41

    I hope the students realize how lucky they are to have this professor

    • @solaaar3
      @solaaar3 11 วันที่ผ่านมา +1

      not really lucky, they paid a fortune to get there..

    • @prithvib8662
      @prithvib8662 11 วันที่ผ่านมา

      @solaaar3 and even still, many who paid get absolutely terrible professors. Finding someone this passionate about teaching is a matter of luck at this point

  • @ananth2006
    @ananth2006 18 วันที่ผ่านมา

    This is a great lecture series! I love how he constantly keeps the big picture in mind, makes retaining this so much easier.

  • @hariprasath7050
    @hariprasath7050 4 หลายเดือนก่อน +4

    I don't know what to say about Professor Chris he's very energetic and amazing professor I ever seen in my life like him actually the hardest subject is probability he teaches just like that in simplest way thanks Stanford giving us opportunity to learn those who aren't Stanford students

  • @Ap-mo7kt
    @Ap-mo7kt ปีที่แล้ว +4

    This course is amazing..the professor is great. This is the only prob course I have taken which keeps me awake throughout the lecture.

  • @comeandsee8275
    @comeandsee8275 3 หลายเดือนก่อน +1

    the best probability professor ever

  • @snehayadav9275
    @snehayadav9275 9 หลายเดือนก่อน +2

    class starts at 2:55

  • @violetashopova3586
    @violetashopova3586 ปีที่แล้ว +2

    Amazing professor... I am surprised though he gave a (kind of) Vann diagram explanation with the SARS problem only at the very end, and should've probably explained the confusion matrix rather than label it non-important

  • @robinhylands69
    @robinhylands69 11 หลายเดือนก่อน +1

    This guy is good.

  • @miosoto
    @miosoto 9 หลายเดือนก่อน +2

    what is the answer for the question given in the end of the lecture

    • @young_money
      @young_money 7 หลายเดือนก่อน +1

      I got this:
      K = Knows the concepts
      C = Correctly answered
      P(K|C) = P(C|K) * P(K) / P(C)
      P(K) = 0.75
      P(C|Kc) = 0.25
      P(Cc|K) = 0.10
      P(Kc) = 1 - P(K) = 1 - 0.75 = 0.25
      P(C|K) = 1 - P(C|Kc) = 1 - 0.25 = 0.75
      (P(C|K) * P(K)) / (P(C|K) * P(K) + P(C|Kc) * P(Kc))
      (0.75 * 0.75) / (0.75 * 0.75 + 0.25 * 0.25)
      = 0.9

    • @Lee-zo3dy
      @Lee-zo3dy 7 หลายเดือนก่อน +2

      @@young_money Sorry, I think this: P(C|K) = 1 - P(C|Kc) = 1 - 0.25 = 0.75 is wrong!
      p(C|K) = 1- p(Cc|K) holds but the above does not holds every time

    • @chamirus1
      @chamirus1 7 หลายเดือนก่อน +4

      K = know the correct answer
      G = gets the answer correct
      We know that:
      P(K) = 3/4 = 0.75
      P(G|Kc) = 1/4 = 0.25
      P(Gc|K) = 1/10 = 0.1
      So:
      P(K|G) = P(G|K)*P(K)/P(G)
      = P(G|K)*P(K)/(P(G|K)*P(K) + P(G|Kc)*P(Kc))
      = (1 - P(Gc|K))*P(K)/((1 - P(Gc|K))*P(K) + P(G|Kc)*(1 - P(K)))
      = (1 - 0.1)*0.75/((1 - 0.1)*0.75 + 0.25*(1 - 0.75))
      ≅ 0.9153

    • @kushaagra098
      @kushaagra098 7 หลายเดือนก่อน

      @@chamirus1 yep this is correct!

  • @4th_wall511
    @4th_wall511 7 หลายเดือนก่อน

    43:24 To the student's point, isn't it the case that P(E|T) = P(T|E) iff P(E) = P(T) and P(E and T) =/ 0?

  • @Lee-zo3dy
    @Lee-zo3dy 7 หลายเดือนก่อน +1

    I think at 37:10 professor did not make it quite clear for probability = 0. The student confused probability with possibility. It is totally ok for thing A that is p(A) = 0 to happen to some extent. Am I right?

    • @kushaagra098
      @kushaagra098 7 หลายเดือนก่อน

      ya, P(A)=0 means that the probability of event A is immeasurable. It does not necessarily mean that it is impossible.

  • @GemmaMiss
    @GemmaMiss ปีที่แล้ว +5

    I’ve rewatched my college lecture 4 times and didn’t understand. I still didn’t really understand until...Netflix. The penny dropped. Lectures need to be started with these kind of examples.
    Thank you Stanford. Picking up for useless lecturers around the world

  • @burnytech
    @burnytech 6 หลายเดือนก่อน

    lovely!

  • @abunapha
    @abunapha 9 หลายเดือนก่อน +3

    To E or not to E? That is the question

  • @vinayak3751
    @vinayak3751 5 หลายเดือนก่อน

    Explaining bayes theorem with poop. Legend.

  • @greielts75331
    @greielts75331 7 หลายเดือนก่อน +1

    This guy is not rigorous.

    • @TheHighestStateOfPotatoChips
      @TheHighestStateOfPotatoChips 4 หลายเดือนก่อน

      @greielts75331 Well, I guess its a good lecture as a first pass intro into Probability. A rigorous one can be the second pass. Do you have a link to a more rigorous lecture?

  • @ikechukwumichael1383
    @ikechukwumichael1383 2 หลายเดือนก่อน

    What a poopy explanation 😅