Hey there! Sign in to join this conversationNew here? Join for free
    Offline

    9
    ReputationRep:
    whats the formula for standard deviation? i googled it and like 50 different variations came up
    Offline

    2
    ReputationRep:
    (Original post by KloppOClock)
    whats the formula for standard deviation? i googled it and like 50 different variations came up
    Name:  ImageUploadedByStudent Room1465652854.026067.jpg
Views: 128
Size:  39.5 KB
    This is the most used formula, but the formula for V and SD is slightly different when you are working with Discrete Random Variables/Normal Distribution. Check the Edexcel S1 summary page at the end of each chapter to be sure.


    Posted from TSR Mobile
    Offline

    9
    ReputationRep:
    I dont get question 4 part d
    https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

    Question is what is the probability of some studying SnDnN given that they study SnN.

    So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

    which = (4/180) / (36/180) = 1/9

    however the answer says its 1/10
    Offline

    3
    ReputationRep:
    (Original post by KloppOClock)
    I dont get question 4 part d
    https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

    Question is what is the probability of some studying SnDnN given that they study SnN.

    So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

    which = (4/180) / (36/180) = 1/9

    however the answer says its 1/10
    There are 40 people who do SnN and of those 40, 4 do all three, so its 4/40=1/10
    Offline

    9
    ReputationRep:
    (Original post by 4nonymous)
    There are 40 people who do SnN and of those 40, 4 do all three, so its 4/40=1/10
    but why isnt it conditional
    Offline

    3
    ReputationRep:
    (Original post by KloppOClock)
    but why isnt it conditional
    Have a look on exam solutions he explains how to work it out.
    Offline

    9
    ReputationRep:
    (Original post by 4nonymous)
    Have a look on exam solutions he explains how to work it out.
    i did he just briefly said what the other guy above said
    Offline

    2
    ReputationRep:
    (Original post by Philip-flop)
    Well you already know that the question is asking what the probability of her phone lasting 133 hours is. Think about it this way....

    P(not need charging after 133 hours)
    = P(L>133 | L>127)
    = _P(L>133)_
    P(L>127)

    ^It's probability after 133 hours because why would she want to charge her phone before her flight is over!

    Hope this helps
    Yeah thanks that helped a lot
    Offline

    9
    ReputationRep:
    when you go to find the sum of x^2, sum of y^2, sum of xy etc. would you get penalised for doing it using your calculator. What I mean is, would you get penalised for not working out the squares of every x and adding them up, because i feel that its easier and quicker to just stick your data into your calc on stat mode, and work it out that way
    Offline

    11
    ReputationRep:
    (Original post by ishaniss)
    when you go to find the sum of x^2, sum of y^2, sum of xy etc. would you get penalised for doing it using your calculator. What I mean is, would you get penalised for not working out the squares of every x and adding them up, because i feel that its easier and quicker to just stick your data into your calc on stat mode, and work it out that way
    Well its always useful to show your method, look at the mark schemes and see if marks are awarded for methods or just answers
    Offline

    0
    ReputationRep:
    What's the difference between being not independent and mutually exclusive?
    Offline

    11
    ReputationRep:
    (Original post by KloppOClock)
    I dont get question 4 part d
    https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

    Question is what is the probability of some studying SnDnN given that they study SnN.

    So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

    which = (4/180) / (36/180) = 1/9

    however the answer says its 1/10
    You've calculated wrong probably due to the venn diagram misleading you

    Remember there is 40 people do S&N not 36

    So P (S&N&D/ S&N) = 4/40
    Offline

    9
    ReputationRep:
    (Original post by physicsamor)
    You've calculated wrong probably due to the venn diagram misleading you

    Remember there is 40 people do S&N not 36

    So P (S&N&D/ S&N) = 4/40
    thank you!
    Offline

    11
    ReputationRep:
    (Original post by KloppOClock)
    thank you!
    No problem, I made the same mistake and I just had to read through it a few times because no solutions were helping me
    Offline

    0
    ReputationRep:
    Hi, I was wondering if anyone could answer a few questions I had:

    1. What sorts of things might we be asked about statistical models and what do we need to know?

    2. What functions of the fx-991ES PLUS calculator can we use in the exam

    3. What's the difference between mutually exclusive events and independent events or is there non?
    Offline

    2
    ReputationRep:
    (Original post by apparently_anerd)
    Hi, I was wondering if anyone could answer a few questions I had:

    1. What sorts of things might we be asked about statistical models and what do we need to know?

    2. What functions of the fx-991ES PLUS calculator can we use in the exam

    3. What's the difference between mutually exclusive events and independent events or is there non?
    1. advaantages and disadvantages i have seen in past pprs
    3. MEE p( a and b) = 0
    Independant: p(a and b) = p(A) times p(B)
    Offline

    3
    ReputationRep:
    (Original post by apparently_anerd)
    Hi, I was wondering if anyone could answer a few questions I had:

    1. What sorts of things might we be asked about statistical models and what do we need to know?

    2. What functions of the fx-991ES PLUS calculator can we use in the exam

    3. What's the difference between mutually exclusive events and independent events or is there non?
    someones already answered 1 and 3 so:

    2. There are a lot of things you can do on your calculator. You can work out:
    mean
    variance
    standard deviation
    sum x^2, sum y^2 etc
    Normal distribution
    Offline

    9
    ReputationRep:
    Effects of coding on Sxx, Syy & Sxy?

    Edit:

    Sxx has the same effect as variance

    Sxy has the same effect as standard deviation
    Offline

    3
    ReputationRep:
    Does anyone have access to the S1 paper from Jan 2016, please?
    Offline

    1
    ReputationRep:
    (Original post by Pink1998)
    Does anyone have access to the S1 paper from Jan 2016, please?
    doesn't exist
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Are unpaid trial work shifts fair?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.