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

    22
    ReputationRep:
    (Original post by Geraer1)
    One thing to clarify: pmcc measures the linear association or linear correlation, because I just saw in a mark scheme which says linear association?
    Definitely linear correlation. However, once you specify the word linear, correlation and association become the same thing. But in general, pmcc and spearman is always correlation and never association. Association is always for contingency tables.
    Offline

    3
    ReputationRep:
    (Original post by L'Evil Wolf)
    is the unbiased estimator proof in our spec?
    If your spec is Edexcel then yes! Its real easy google it and memories it!
    Offline

    22
    ReputationRep:
    (Original post by Music With Rocks)
    Is the spearman's rank wrong for June 2013 R Q3? They appear to have ordered the employees completely wrong!?

    Attachment 537785
    The order of ranking does not matter as long as it consistent.
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Definitely linear correlation. However, once you specify the word linear, correlation and association become the same thing. But in general, pmcc and spearman is always correlation and never association. Association is always for contingency tables.
    Ah okay thanks and spearman correlation coefficient measures the ranking between 2 variables. It doesnt necessarily needs to be linear. Is that correct?
    Offline

    3
    ReputationRep:
    (Original post by Music With Rocks)
    Is the spearman's rank wrong for June 2013 R Q3? They appear to have ordered the employees completely wrong!?

    Attachment 537785
    No they've ordered both from smallest to largest, So for A the 2 means 2nd smallest in employee's and the 1 means 1st smallest in Population.
    Offline

    22
    ReputationRep:
    (Original post by Geraer1)
    Ah okay thanks and spearman correlation coefficient measures the ranking between 2 variables. It doesnt necessarily needs to be linear. Is that correct?
    Correct.
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Correct.
    Thanks Zacken for clarifying so many things!
    Offline

    2
    ReputationRep:
    Name:  Screen Shot 2016-05-24 at 20.41.04.png
Views: 95
Size:  173.0 KB
    For this question, do we actually need to approximate 15 to 15.5 ?
    Offline

    3
    ReputationRep:
    (Original post by paradoxequation)
    Haha. Also I have a question regarding the 2015 question about the difference in the standard errors between the children and the staff, could you explain it to me? I'm a bit lost on that one. Thanks.
    Yeah I don't understand that, nor the markscheme and nor does any of my teachers so it's one of those things Edexcel puts in and your required to guess the examiners thoughts!

    Crops up in Edexcel physics alot!
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Children and adults have vastly different weights, so if you consider them in the same category, the variance from the mean is going to be quite large given how different their weights are. So the variance is larger, hence the standard deviation is larger and hence the standard error is larger since \text{s.e} = \frac{\sigma}{\sqrt{n}}. i.e: it is proportional to standard deviation.

    However, if you consider the children and adults in two separate categories, the variances from the mean are much smaller.
    Thank you!
    Offline

    22
    ReputationRep:
    (Original post by anndz3007)
    Name:  Screen Shot 2016-05-24 at 20.41.04.png
Views: 95
Size:  173.0 KB
    For this question, do we actually need to approximate 15 to 15.5 ?
    Yes.

    (Original post by Inges)
    Yeah I don't understand that, nor the markscheme and nor does any of my teachers so it's one of those things Edexcel puts in and your required to guess the examiners thoughts!

    Crops up in Edexcel physics alot!
    No, it makes total sense. See my answer above.

    (Original post by paradoxequation)
    Thank you!
    You're welcome.
    Offline

    2
    ReputationRep:
    (Original post by Inges)
    No no, Sorry I think I misunderstood your question. You have to show the way you obtained the expected frequencies in a table like they have set out showing your Row total x Column total / grand total. then the expected frequency. After that, you can do what you said.

    This has been the case in a few papers, and some papers they just show the expected frequency without calculation. I haven't noticed a pattern in when they want you to show the working but id show it anyway to be safe!
    Oh I see Thanks
    Offline

    3
    ReputationRep:
    (Original post by Zacken)
    Yes.



    No, it makes total sense. See my answer above.



    You're welcome.
    That made so much sense, Thanks alot!
    Offline

    3
    ReputationRep:
    (Original post by Zacken)
    Yes.



    No, it makes total sense. See my answer above.



    You're welcome.
    Just wondering how you got around to that explanation since the mark scheme doesn't explain it anywhere near how you did!
    Offline

    3
    ReputationRep:
    (Original post by Geraer1)
    Oh I see Thanks
    Anytime!
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Yes.



    No, it makes total sense. See my answer above.



    You're welcome.
    but why ? the first line was 15 and follow up is 15-19.5, why would you turn it to 15.5
    Offline

    22
    ReputationRep:
    (Original post by Inges)
    Just wondering how you got around to that explanation since the mark scheme doesn't explain it anywhere near how you did!
    AFAICS, It's precisely what the markscheme says just worded in a slightly less obscure and jargon-cluttered way.
    Offline

    22
    ReputationRep:
    (Original post by anndz3007)
    but why ? the first line was 15 and follow up is 15-19.5, why would you turn it to 15.5
    Oh sorry, yeah. Should have read it properly, you wouldn't need to, there's no gap there.
    Offline

    3
    ReputationRep:
    (Original post by Zacken)
    AFAICS, It's precisely what the markscheme says just worded in a slightly less obscure and jargon-cluttered way.
    I see, thanks anyway
    Offline

    2
    ReputationRep:
    (Original post by Zacken)
    Oh sorry, yeah. Should have read it properly, you wouldn't need to, there's no gap there.
    this is what confuse me, cus in the madas answer, he rounded it up to 15.5 and his answer is completely different to mine ._.
    http://www.madasmaths.com/archive/ma...ess_of_fit.pdf
    Q1, continuous
 
 
 
  • 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
    What's your favourite Christmas sweets?
  • 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.