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    S1 is killingg me! the language of the questions is complicated
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    screwed up m1 yesterday. now i have to work harder for s1, at least 85/100
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    (Original post by Cynical_Smile01)
    You have nothing on me mate: Stats, Decision, Economics, Politics. All 1.5 hours long. 6 hours of exams in one day. That is my Friday. ****ing myself about it.

    I'm counting on Stats or Decision. Mechanics was horrid yesterday.

    Posted from TSR Mobile
    Oh wow! And I thought I had it bad haha.

    Yeah mechanics was a weird old thing yesterday. Mad at myself because that's my strongest applied module and I lost some ridiculous marks just because of exam nerves, like equating the wrong components in the vectors question. Surprisingly I got the hard part rift but the easy part wrong haha.

    Anyway, I wish you the best of luck for Friday, and indeed the rest of your exams. May the mass x acceleration be with you (too far?)




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    Any predictions of what may come up in the exam?
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    (Original post by liowwc)
    screwed up m1 yesterday. now i have to work harder for s1, at least 85/100
    uchhh same, M1 was ridiculous!!! Need at least 90 UMS now in this fingers crossed!
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    anyone here quite strong at probability/normal distribution ? need help quite badly...
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    Anyone else finding the Solomon Papers for S1 ALOT easier than the real past paper questions (especially from 2011 onwards)? Baffling I hope Fridays exam doesn't have any weirdly worded question I can't think straight in such pressure!
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    RIGHT. i need some serious help here - firstly with Normal Distribution - how the **** do solve the ones where it doesn't give you the mean or standard deviation, but does give you two probabilities ( like for example P(X < 25 ) = 0.15 ) ? my teacher has NEVER taught me how to do this and ive just seen it on an exam question lol
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    (Original post by Fas)
    RIGHT. i need some serious help here - firstly with Normal Distribution - how the **** do solve the ones where it doesn't give you the mean or standard deviation, but does give you two probabilities ( like for example P(X < 25 ) = 0.15 ) ? my teacher has NEVER taught me how to do this and ive just seen it on an exam question lol
    Simultaneous equations. Use Z = (X-μ)/(σ) so then we have P(Z< (25-μ)/σ) = 0.15

    Using your tables, this is the same as saying (25-μ)/σ = -1.0364

    This is one of the equations. You would be given something else like P(X > 60 ) = 0.25 and we would find another equation the same way.

    Then just use GCSE skills. Make σ or μ the subject and sub into the other equation which should give you one of the values. Sub that value back into original equation to find the other value.
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    Please tell me this thread is for Edexcel or any other exam board except for OCR. :confused:
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    (Original post by Themiddleone)
    Please tell me this thread is for Edexcel or any other exam board except for OCR. :confused:
    Edexcel here :P
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    My past papers marks have ranged from 52 - 75 today, in an order of: 52, 75, 54, 69... Some of the questions on S1 are just intolerable.
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    When finding the median on a stem and leaf diagram, sometimes I've seen that you need to add 1 and divide total by 2 then find the middle of two values, but sometimes the answer is given by just taking e.g. the 14.5th value as the 15th value and not midway between the 14th and 15th value - does anyone understand what I mean and know when to do what?

    Do you do the half way between values only when the total number is even, if that makes sense?
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    (Original post by Satanel)
    Some of the questions on S1 are just intolerable.
    This. In one paper I could get full marks and then in another I will be just scraping the A grade.
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    (Original post by Kreayshawn)
    Do you do the half way between values only when the total number is even, if that makes sense?
    Just add 1 to the amount of numbers and divide by 2 for the median. You can't go wrong there. Don't make it complicated for yourself.
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    (Original post by Fas)
    RIGHT. i need some serious help here - firstly with Normal Distribution - how the **** do solve the ones where it doesn't give you the mean or standard deviation, but does give you two probabilities ( like for example P(X < 25 ) = 0.15 ) ? my teacher has NEVER taught me how to do this and ive just seen it on an exam question lol
    You would need a mean to do what you are asking, or a standard deviation. Perhaps you're not on a standard deviation question, its easy to get confused. Have a look on 'exam solutions' and go through his tutorials, always seems to explain things perfectly.
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    (Original post by Fas)
    RIGHT. i need some serious help here - firstly with Normal Distribution - how the **** do solve the ones where it doesn't give you the mean or standard deviation, but does give you two probabilities ( like for example P(X < 25 ) = 0.15 ) ? my teacher has NEVER taught me how to do this and ive just seen it on an exam question lol
    You would have to then set up two equations in terms of the mean (m) and the standard deviation (sd). In this question you would always be given the probability and what it is, ie probability of it being less than 700ml or something

    So what you would do is go about standardising it p(x-m)/sd for both sides and then you will eventually emerge with two equations which you would then solve simultaneously to find the mean and then the standard deviation (or visa versa)

    That's a really bad explanation but if you tell me what paper it is perhaps I can explain it better. I'm sitting here with every single paper in front of me so come at me lol


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    (Original post by B-Stacks)
    Just add 1 to the amount of numbers and divide by 2 for the median. You can't go wrong there. Don't make it complicated for yourself.
    I usually do this but on some occasions the mark scheme gives the answer as a decimal - a value half way between the two middle numbers
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    (Original post by Kreayshawn)
    I usually do this but on some occasions the mark scheme gives the answer as a decimal - a value half way between the two middle numbers
    When working those things out, you have to go by whether or not your answer is an integer value or not.

    For example, of there was a sample of 120 students, the middle value would be the 60.5th value, simply because 120/2 is 60 which is a whole number, therefore you need to do the 60th value + the 61st value and divide them by 2.
    Similarly, if there were 121 students, you would simply divide by 2 and round up, as 121/2 is 60.5 which is obviously not a whole number.

    Super main point: if n/2 is an integer, do the middle value of n and n+1. If n/2 isn't an integer, simply round up and read off that value.

    I hope that helps, and guys if I'm not making any sense please tell me and I'll shut up and go to sleep lol. Thanks

    EDIT: This only applies to finding quartiles for discrete data. For continuous data, it isn't necessary to do any rounding. Forgot to add that in, sorry! Thanks to jehearo for pointing that out
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    (Original post by lebron_23)
    You would have to then set up two equations in terms of the mean (m) and the standard deviation (sd). In this question you would always be given the probability and what it is, ie probability of it being less than 700ml or something

    So what you would do is go about standardising it p(x-m)/sd for both sides and then you will eventually emerge with two equations which you would then solve simultaneously to find the mean and then the standard deviation (or visa versa)

    That's a really bad explanation but if you tell me what paper it is perhaps I can explain it better. I'm sitting here with every single paper in front of me so come at me lol


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    it's ok i managed to get the grip of it using THE BEAST that is ExamSolutions and their youtube video about it haha - many thanks for replying though and to circa1801 and Air1337 aswell !

    gonna have a crack at January 2012 now - but these S1 papers are ****ing weird , my marks vary significantly - that said ive only done three papers haha
 
 
 
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