Edexcel S3 - Wednesday 25th May AM 2016

Reply 1080

econam

11

Original post by Zacken

Yes. June 2013.

Thanks! done so many questions im losing track lol

Reply 1081

Music With Rocks

9

Original post by Zacken

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

Original post by Inges

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.

Thank you, I was just being a complete div :s-smilie:

Reply 1082

Inges

3

Original post by Music With Rocks

Thank you, I was just being a complete div :s-smilie:

No problem, read all the questions and answers on here as your last resort & youll smash this don't worry at all!

Reply 1083

economicss

3

Original post by Inges

If your spec is Edexcel then yes! Its real easy google it and memories it!

Please could you post this proof, can't seem to find it online, do we definitely need to be able to prove it? Thanks :smile:

Reply 1084

Rkai01

6

What's the rule about mode mean and median in relation to positive and negative Skewness?

Reply 1085

Inges

3

Original post by Rkai01

What's the rule about mode mean and median in relation to positive and negative Skewness?

Mean<Median<Mode = Negative
Mean>Median>Mode = Positive

Not sure how to learn it easily, i just learnt it how it is

Reply 1086

economicss

3

Original post by economicss

Please could you post this proof, can't seem to find it online, do we definitely need to be able to prove it? Thanks :smile:

@Zacken Please help, do we need to know this proof, and if so what is it in it's simplest form please? Thanks :smile:

Reply 1087

kennz

8

Original post by Rkai01

What's the rule about mode mean and median in relation to positive and negative Skewness?

mode<median<mean for positive
mode>meadian>mean for negative

I remember it by the mean being the prime method used by people/statisicians so if the mean is highest, its positive

Reply 1088

kennz

8

https://869d950bf149eefd5cd2652b400160ceb38ca5c7.googledrive.com/host/0B1ZiqBksUHNYVGVDMmVJYzVnRnc/June%202010%20QP%20-%20S3%20Edexcel.pdf
Question 3b, why is the variance the standard error and not 16 times the variance?

Reply 1089

Inges

3

Original post by economicss

Please could you post this proof, can't seem to find it online, do we definitely need to be able to prove it? Thanks :smile:

I'm gonna write it out on a piece of paper and upload it in a minute.

Reply 1090

Euclidean

11

I'm trawling through this thread and getting freaked out by people saying 'total error' and using terminology that isn't in the textbook so I'm gonna call it a day with this thread and revisit it after the exam tomorrow.

Good luck to everyone :smile:

Reply 1091

Rkai01

6

Original post by kennz

mode<median<mean for positive
mode>meadian>mean for negative

I remember it by the mean being the prime method used by people/statisicians so if the mean is highest, its positive

With relation to whether it can be from a normal distribution, is a positive Skewness indicating it can be from a normal distribution?

Reply 1092

anndz3007

2

Original post by kennz

https://869d950bf149eefd5cd2652b400160ceb38ca5c7.googledrive.com/host/0B1ZiqBksUHNYVGVDMmVJYzVnRnc/June%202010%20QP%20-%20S3%20Edexcel.pdf
Question 3b, why is the variance the standard error and not 16 times the variance?

It asked Find the probability that the mean of these results is within 0.3 mm of w. and mean would be 16/16 square which make it /16

Reply 1093

kennz

8

Original post by anndz3007

It asked Find the probability that the mean of these results is within 0.3 mm of w. and mean would be 16/16 square which make it /16

thank you, completely misread it, I thought thats what it had to be but I couldnt see the mean in the question haha

Reply 1094

Kevin De Bruyne

OP

21

Original post by Euclidean

I'm trawling through this thread and getting freaked out by people saying 'total error' and using terminology that isn't in the textbook so I'm gonna call it a day with this thread and revisit it after the exam tomorrow.

Good luck to everyone :smile:

Good luck! :rave:

Reply 1095

Zacken

22

Original post by economicss

@Zacken Please help, do we need to know this proof, and if so what is it in it's simplest form please? Thanks :smile:

Pretty sure the textbook says the proof isn't examinable.

Reply 1096

Zacken

22

Original post by Euclidean

I'm trawling through this thread and getting freaked out by people saying 'total error' and using terminology that isn't in the textbook so I'm gonna call it a day with this thread and revisit it after the exam tomorrow.

Good luck to everyone :smile:

Sound.

Good luck. :smile:

Reply 1097

Inges

3

Original post by economicss

Please could you post this proof, can't seem to find it online, do we definitely need to be able to prove it? Thanks :smile:

Its not letting me upload it so i put it on imgur.

Heres the link : http://imgur.com/wojNvaa

Reply 1098

paradoxequation

2

For part d, if you use the Variance formula Var(X-Y)=Var(X)+Var(Y) you get 6sigma^2/5 which is incorrect. The actual variance was 4sigma^2/5 and I understand how to get there.

Am I correct in saying we do not use the variance formula because U1 and Ubar are from the same sample? Thanks.

Original post by paradoxequation

For part d, if you use the Variance formula Var(X-Y)=Var(X)+Var(Y) you get 6sigma^2/5 which is incorrect. The actual variance was 4sigma^2/5 and I understand how to get there.

Am I correct in saying we do not use the variance formula because U1 and Ubar are from the same sample? Thanks.

It's because

U_1

and

\bar{U}

are not independent. The formula you quoted are only for independent random variables

X,Y

. They are not independent because they come from the same sample, but the important thing here is that they are not independent.

Edexcel S3 - Wednesday 25th May AM 2016

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