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S1 May 2012 - Post Exam Thread - Paper and Solutions in the FIRST POST

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Original post by Arsey
You ought to get all the marks for saying mean as it is almost symmetrical with no obvious outliers.


What if you didn't mention the skew, but said that it was grouped data and each group had 30 or more cars in, therefore no obvious outliers, therefore mean?
Reply 681
Avatar for Arsey
Arsey
OP
10
Original post by Prolite
It will be a follow through question as long as you referred back your answer you will get mark you won't be penalised twice

I hope you wrote mean = median or something to reference back or something similar in words



I am the teacher :tongue: am private candidate tbh I'd rather retake all mechanics modules instead of retaking s1 also if u ask for paper u can't send for remark isn't it



no, you can request a copy of your paper, see if there is a problem in with the marking, if so, request a remark.
(edited 11 years ago)
Original post by When you see it...
What if you didn't mention the skew, but said that it was grouped data and each group had 30 or more cars in, therefore no obvious outliers, therefore mean?


Why the neg?
In case anyone likes flash cards, I made these when I took the exam last year:

http://flashcarddb.com/cardset/133177-s1-flashcards

EDIT: Just realised you've all taken the exam already - my bad.
(edited 11 years ago)
Original post by When you see it...
What if you didn't mention the skew, but said that it was grouped data and each group had 30 or more cars in, therefore no obvious outliers, therefore mean?


Can someone confirm that this is wrong and explain why? I don't see why it is getting negs, it seems reasonable to me (although maybe you should use median just in case if you are uncertain about outliers...).
Reply 685
Avatar for Livourabi
Livourabi
Thank you! YAAAAY! I got the histogram question right, that was very tricky. I think they may lower boundaries slightly due to the fact that that question was so hard and it was worth something like 14 marks.

I THINK I got 73. Hopefully!!!!
Reply 686
Avatar for Napdull
Napdull
I didn't sit the paper and I'm not a teacher but on Q5 e) I would have said the median is best because of the skew.
But couldn't it be argued that the 30 cars in the 10-15mph range (just 6.6% of the sample) are all outliers because no data was registered in the 15-20mph category? An outlier being a part situated away from a main or related body?

It then brings into question the reliabilty of this data. Would these slow cars have travelled faster if they hadn't been stuck behind a farm tractor or steamroller?
If we then ignore this slow car data as being unreliable, the positive skew then gets even bigger (mean 30.89mph versus median 28.75mph) giving even more justification to use the median.
Although normally it is the outliers that cause the skew and when you remove them the skewness is reduced.
Can you now say though that to say the average motorist breaks the speed limit if allowed (30.89mph) when clearly more than half do not? I don't think so, so for this question I don't think you can ever say the mean can be used because as there are no outliers.

I'm also not certain you can argue the median can be used because there are outliers. So not only was this a nasty question it was also a nasty set of data for the students to interpret. I hope the examiners go easy on the marking.
Reply 687
Avatar for jadzirt
jadzirt
hey arsey, if the paper required more thought than normal, then wouldnt the grade boundaires be a lot lower. Jun 2010 wasnt much harder and for that 90 UMS was only 62?! im fretting about this exam :/
I really liked this paper except for the normal distribution question part c I got so confused. Will I lose a mark for not drawing a line on my graph I drew?
Reply 689
Avatar for Giggy88
Giggy88
17
Hey people

For showing mutually exclusive results I've got 2 answers

1. BnW = 0
2. TnW = 0

Aren't they both right ?!
Reply 690
Avatar for gshock
gshock
6
Original post by Killer_94
no it doesn't matter... its the same thing


mehh aced that paper anyway
Question 5 was the only tricky question tbh
How many marks do you think i'd get given for the last two parts of the question involving the normal distribution function, if instead of using the small table including probabilities greater than, i took an average of two of the values from the larger table?

I know they usually would allow for some method marks or something
Reply 693
Avatar for icim
icim
do you guys think i will get a mark for standardising in (b) part of question 6??
what do you guys reckon will be 53 to 58 raw marks in UMS?
Original post by otrivine
what do you guys reckon will be 53 to 58 raw marks in UMS?


Otrivine, forget about S1 now, wait for the result.

You can't go back in time and change it, so don't think about it.
Original post by raheem94
Otrivine, forget about S1 now, wait for the result.

You can't go back in time and change it, so don't think about it.


hey how are you :smile:

i know but i am estimating what i think i got? i mean what you think that will be though raheem
Original post by otrivine
hey how are you :smile:

i know but i am estimating what i think i got? i mean what you think that will be though raheem


I am fine, what about you?

Estimating won't do you any favor, forget about exams as they are now over!

I don't have much idea about grade boundaries so can't make a prediction.
Original post by otrivine
what do you guys reckon will be 53 to 58 raw marks in UMS?


58 raw marks will probably be a mid B
Original post by raheem94
I am fine, what about you?

Estimating won't do you any favor, forget about exams as they are now over!

I don't have much idea about grade boundaries so can't make a prediction.


ok thanks for helping me :smile:

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