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

1. (Original post by heyitskim)
For S1, there's types of questions where they state a number has been added or reduced. And then it asks you to state the effect made on the standard deviation, mean, IQR etc? Can someone please explain to me how to do these type of questions😩 I don't understand

You put your hand up in the exam and ask the invigilator to come over, and then you ram your fist up their arse.
2. (Original post by iMacJack)
But, why -0.25? Why not -0.01 or whatever? I'm being really stupid here I'm sure
You need to read the question. The top 25% of the candidates get a merit.

The top 75% of the candidates get a pass. This 75% includes the 25% getting a merit.

So the middle 50% between 25% and 75% are candidates who pass but don't get a merit.

It has nothing to do with "even if they got 74% they'd pass", the question says absolutely nothing about the marks of the candidates (so how on earth can you say if they got 74% they'd pass??? You don't know that...), simply their ranks. The top 75% get a pass, the top 25% get a pass and a merit. So the 75% - 25% = 50% middle get a pass but not a merit.
3. (Original post by Mina_)
I dont understand the logic behind this either
See my post above.
4. (Original post by Bloom77)
BOX PLOT QUESTION HELP

When you work out outliers
But none of the data falls into those outliers
Then what is your highest and lowest numbers? Would it be the numbers on the data or the outliers?

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5. Numbers from the data
6. how does coding affect the pmcc and mean and so on
7. I'm pretty sure they accept both. I always do the highest and lowest values of the given data, but they draw both in mark schemes so either should be fine.
8. was hoping S1 was gonna boost my mark... doesn't look too good

9. Can someone explain part (d)
10. (Original post by iMacJack)
Okay but what I'm saying is even if they got 74% they'd still pass, but not get a merit, right? I'm a little bit confused...

The people from 25% till the end of the whole box plot are passing. So, from the Q1 to the Q3 is the amount of people passing and from Q3 till the end is the amount of people getting merit. The number of people ONLY passing, is therefore the amount from Q1 to Q3, which is (75-25) = 50%.
11. I dont understand part d.
12. (Original post by Mina_)

Can someone explain part (d)
What is the probability of passing the test overall?

P(pass test first time) + P(fail first time)P(pass second time) = 0.95

So p + (1-p)(p-0.2) = 0.95

You need to think this through, this is GCSE level stats.
13. So I just did the S1 (IAL) Jan 2016 paper and didn't even have time to finish the last question!! I am definitely screwed if we have a similar exam tomo! I just couldn't work through it quick enough
14. (Original post by SweetChilliCake)
I dont understand part d.
E((X+1)^2) = E(X^2 + 2X +1) = E(X^2) + 2E(X) + 1, now plug in what you know about E(X^2) and E(X).

Also, in the future, be more specific about what you do/don't udnerstand as well as your attempt and your own thoughts...
15. if i use n+1/2 to find median for discreet or continuous data, will i always get the same answer?
16. (Original post by Zacken)
E((X+1)^2) = E(X^2 + 2X +1) = E(X^2) + 2E(X) + 1, now plug in what you know about E(X^2) and E(X).

Also, in the future, be more specific about what you do/don't udnerstand as well as your attempt and your own thoughts...
Ahh so you expand the brackets first 😃. Thanks.
17. (Original post by SweetChilliCake)
Ahh so you expand the brackets first 😃. Thanks.
Yes.
18. I've got a few questions if anyone can answer them:
1) for the regression line how man sig figs do we do it to
2. when drawing out the box plots, how should i show the maximum point in which we worked out q3+(1.5*IQR)
19. (Original post by Setarehp)
Does anyone know how to do question 4 Excercise 5f in the s1 textbook?
You'll get more luck posting a picture of the question and what you've tried and what specific problems you have with the question.
20. (Original post by HeenaChowdry)
I've got a ew questions if anyone can answer them:
1) for the regression line how man sig figs d we do it to
2. when drawing out the box plots, how should i show the maximum point in which we worked out q3+(1.5*IQR)
1) 3 sig figs. But all working previous to the final answer should be to as much accuracy as possible, only round to 3 sig figs at the end.

2) use asterisks to denote the outliers.

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