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

How is e(r) o.45
I thought it was coding ??

I got r = -0.753 because I used the calculator value of Syy (716 with decimals) and not the given value of Syy (716 to 3sf)

Will I lose marks? Did anyone else get that?

Just a quick question guys, I do As maths and fm, if I did badly in s1 and good in m1 would s1 be moved to fm and m1 be moved to maths?

Lmaolol my wiggle comment got 6 likes yours got one get wrecked

Assuming it's the correct value, you won't lose marks. If the rounded and non-rounded values produce different answers, the mark scheme should allow a range that accommodates both.

But how do I know its right?

So I got Syy = 716 with a load of decimals after then rounded to 3sf like they asked.

Then when calculating r I plugged my value that had decimals

So I got Syy = 716 when it was rounded to 3sf how do I know if its right or not

SD will not change! SD is root of sum of X - X bar divided by n. So as X- X bar is O is this case so sum of X-X bar do not change! so SD remains the same!

As long as you used the correct method and it is clear you got 716 when rounded you will get the marks I think.

Can anyone remember the value of Sxy in one of the questions? It gave you the sum of X y and the sum of X I think?


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Assuming it's the correct value, you won't lose marks. If the rounded and non-rounded values produce different answers, the mark scheme should allow a range that accommodates both.

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The exam board will arrange your applied units to give you the best scores in both. For example, if you got an A in M1, B in S1 and A in D1, accompanied by two strong As in C1 and C2 and perhaps a B in FP1; they will put the B for S1 with C1 and C2 to still give you an A, thus leaving the As to go with FP1 forming your FM grade.

Nope, the mean stayed the same. If you add something that is the mean, it's going to stay the same. Checking on the calculator only confirms the assumption.

The standard deviation does, however change. I believe it decreases as you are reducing the spread of data in this circumstance.

basically guys for the diner question i got 17 people, is this correct and if not what was it and why?
cheers

Can you clarify how to calculate E(R)?

Yeah, you had to work backwards, so sd^2 + mean^2 = sum of fy^2 / sum of f ,
multiply 'sd^2 + mean^2' by sum of f , giving you sum of y^2
then to get y (as opposed to the mean) multiply the mean on y by the frequency (I think it was like 58x8)
then put those in your Syy equation : sum(y^2) - (58x8)^2/8

I don't remember the answer, but thats what I did :P
Seemed like a lot of working for just one mark ...