Edexcel S1 - 15th June, 2016 [Exam Discussion]

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what you didn't know about mean<median = negative skew ?

besides, it will tell you if you need to use this, otherwise learn page 67 of the textbook

Well I thought the mode thing was needed as well :/

Reply 461

thelegend99

Original post by JT423

Yes, any way of proving it's a positive skew is valid. The mark scheme are using: IF
Mean<Median<Mode-- Negative skew
Mean=Median=Mode-- Symmetrical (no skew)
Mean>Median>Mode-- Positive skew

Gotcha, thanks!

Reply 462

miranda_1998

why am i sat reading this instead of actually revising fgs

Reply 463

thelegend99

Original post by anndz3007

mean > median >mode => postive skew
im not sure about your method cus i dont usually use it, only if the question gives you the formula, but the mark scheme allows it for alt so it wont be the case

Mark scheme doesn't say specifically, but apparently any valid method that proves it is right. Thanks!

In in in in. :woo:

Is there no June 2015 (R) paper?

Also, wonder what the chances of statistical modelling coming up.. I don't really know it that well

Reply 466

Siddhart1998

Original post by JT423

the method you used is right. 0.0875=7/80
however how did you get 0.25 for P(b/\c) (maybe venn diagram was wrong). P(b/\c) is also 7/80 (4+3/80) so as they're equal, they're statistically independant

I got 1/4 for p(b//c)
because 28 people do chem. And out of these 28, 7 of them do bio so
7/28 = 1/4.
My Venn was right? I'm probably making a really silly misconception idk

Reply 467

JT423

Original post by Siddhart1998

I got 1/4 for p(b//c)
because 28 people do chem. And out of these 28, 7 of them do bio so
7/28 = 1/4.
My Venn was right? I'm probably making a really silly misconception idk

there are 80 people in the study, not 28, hence the probability of doing both is 7/80..

Reply 468

Siddhart1998

Original post by Uberphuq

Is there no June 2015 (R) paper?

Also, wonder what the chances of statistical modelling coming up.. I don't really know it that well

Just write
-helps improve understanding of real world problem
-simplifies real world problem
-real world problem can be analysed

Reply 469

miranda_1998

do we have to know the process of statistical modelling???

Reply 470

Electrify

Is there a summary for what affects PMCC, standard deviation, mean and quartiles?

Reply 471

Exavior

Can someone explain question 5b on the January 2016 IAL paper. I don't really know how to use given that with normal distribution. I thought that if it is the probability of getting a medal given the probability of a certificate it would be P(M/C)=P(MnC)/P(C)
So I get that the probability of the Certificate is 0.0446 but how do I find the intersection between certificate and medal? The answer just uses the probability of getting a medal over the probability of getting a certificate P(M)/P(C) but I don't get why P(M)=P(MnC) ???
Thank you :s-smilie:

Reply 472

tazza ma razza

67 - 69 for 90 UMS i reckon

Reply 473

Avocado2002

Original post by miranda_1998

do we have to know the process of statistical modelling???

Yes. There are 7 stages.

Reply 474

Jack_Linaker

Original post by angellll

Guys, do you know where I could possibly get the June 2015 paper from?

Here.

s1june2015.pdf304.7KB

Reply 475

tazza ma razza

Original post by neil20143

Don't lie, you can't have finished a stats paper in less than 30 minutes, even if you got 70/75!

i'll let you in on a little secret - having a graphical calculator with certain settings allows you to solve varience / normal distrubutions and do basic probability faster than what I can do without it...

(edited 7 years ago)

Reply 476

LivToBe

Original post by miranda_1998

do we have to know the process of statistical modelling???

yes

Reply 477

tazza ma razza

Original post by Electrify

Is there a summary for what affects PMCC, standard deviation, mean and quartiles?

quartiles aren't affected by a general addition/removal of data - it depends on the value eg if it is below/above the mean/median etc (easiest to figure out)

for the mean, adding/subtracting affects the mean. multiplying i think does (would need an example to confirm this)

for varience (SD^2) multiplying/dividing affects it ie multiplying by 2 leads to it increasing by 4 (I am pretty sure)

PMCC nothing affects it