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Edexcel S3 - Wednesday 25th May AM 2016

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Reply 1060
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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!
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!?

JUNE 2013 R q3.jpg


The order of ranking does not matter as long as it consistent.
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?
Reply 1063
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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!?

JUNE 2013 R q3.jpg


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.
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.
Original post by Zacken
Correct.


Thanks Zacken for clarifying so many things!:biggrin:
Screen Shot 2016-05-24 at 20.41.04.png
For this question, do we actually need to approximate 15 to 15.5 ?
Reply 1067
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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!
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 s.e=σn\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!
Original post by anndz3007
Screen Shot 2016-05-24 at 20.41.04.png
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.
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
Reply 1071
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Original post by Zacken
Yes.



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



You're welcome.


That made so much sense, Thanks alot!
Reply 1072
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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!
Reply 1073
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Original post by Geraer1
Oh I see Thanks


Anytime!
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
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.
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.
Reply 1077
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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
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/maths_booklets/statistics/goodness_of_fit.pdf
Q1, continuous
Original post by anndz3007
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/maths_booklets/statistics/goodness_of_fit.pdf
Q1, continuous


I don't think he was correct in doing so.

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