[Rls1412]

Hey does anyone know whether you get your task 2 back when you do your task 3 and if you get task 2 back can you change your answers to it?
Thanks

[jessplease]

(Original post by Rls1412)
Hey does anyone know whether you get your task 2 back when you do your task 3 and if you get task 2 back can you change your answers to it?
Thanks

Nope if they see you writing on it i think you get disqualifiedd

Edit: why the neg lol? You get the task back but you can't write on it

[AbuzarA]

Anyone got tips for the respiration ISA?

[EffKayy]

(Original post by jessplease)
Nope if they see you writing on it i think you get disqualifiedd

Edit: why the neg lol? You get the task back but you can't write on it

No.
This didnt apply last year for the AS empa. We weren't told that we couldn't write on it..... so.

[handsome7654]

(Original post by smart girl)
i have a casio scientific calculator and for that i calculate s.d by:
mode
2
1
(enter all the readings)
ac
shift
1
5
4

Thankyouu that is a much easier way of doing it!
You really are smart, smart girl!

[raveen789]

Anybody else find task 3 of BIO6X hard or ambiguous? i found it quite challenging and ambiguous and i have no idea how well I have done :/

[broken_rose]

AHHHHHHH I do NOT want to do my empa tomorrow
Panicking just a little... Good luck to anyone doing it tomorrow too

[raveen789]

(Original post by broken_rose)
AHHHHHHH I do NOT want to do my empa tomorrow
Panicking just a little... Good luck to anyone doing it tomorrow too

how did you find it?

[olliec9492]

i need help, can anyone explain the 3 statistical tests you need to know for the EMPA. i cant even remember them all: chi-squared, spearman rank and '?'. but even then i cant remember for the life of me what they mean. any help would be appreciated.

[paul272]

when calculating standard deviation is it, "n", or "n-1". also, if i do use "n-1", does that mean when i calculate standard error, it equals "standard deviation divided by root n-1", or just "root n"

[maxpark3r]

we got taught it for biology as being Sqrt(sum of(x-mean)^2)/(n-1))

[Revd. Mike]

(Original post by paul272)
when calculating standard deviation is it, "n", or "n-1". also, if i do use "n-1", does that mean when i calculate standard error, it equals "standard deviation divided by root n-1", or just "root n"

n if it's the whole population, n-1 if it's a sample.

[thegodofgod]

(Original post by paul272)
when calculating standard deviation is it, "n", or "n-1". also, if i do use "n-1", does that mean when i calculate standard error, it equals "standard deviation divided by root n-1", or just "root n"

I honestly don't get the reasoning behind using 'n-1' - it just invalidates the results, as the standard deviation is shown to be smaller that what it actually is... - sometimes I just don't understand Biology

The 'n' method was used in Maths (Edexcel S1) for standard deviation.

And yes, it would be logical to use 's / sqrt (n-1)' if you are using 'n-1' for standard deviation, in order to be systematic

[Revd. Mike]

(Original post by thegodofgod)
I honestly don't get the reasoning behind using 'n-1' - it just invalidates the results, as the standard deviation is shown to be smaller that what it actually is... - sometimes I just don't understand Biology

See my post above

[thegodofgod]

(Original post by Revd. Mike)
See my post above

But how does 'n-1' take into account for the fact that it's just a sample, and not the whole population

Do you know of any derivation proofs for the formula? It'll be easier for me to understand

[Revd. Mike]

(Original post by thegodofgod)
But how does 'n-1' take into account for the fact that it's just a sample, and not the whole population

Do you know of any derivation proofs for the formula? It'll be easier for me to understand

I'm not sure exactly how it works I'm afraid, I'm not that mathematical a person. I'm sure there's info online though.

Basically it reflects that in a sample the SD will be smaller than in the entire population.

[thegodofgod]

(Original post by Revd. Mike)
I'm not sure exactly how it works I'm afraid, I'm not that mathematical a person. I'm sure there's info online though.

Basically it reflects that in a sample the SD will be smaller than in the entire population.

I'm not really a mathematical person either, I just like looking at pretty proofs

If you've got a representative and unbiased sample though, shouldn't the SD remain constant?

[Revd. Mike]

(Original post by thegodofgod)
I'm not really a mathematical person either, I just like looking at pretty proofs

If you've got a representative and unbiased sample though, shouldn't the SD remain constant?

In an ideal world perhaps, but how often is that the case? In any sample, the statistics will never be as representative as they are for the whole population.

[paul272]

Just wanted to ask, what sort of conclusion would I write, if my confidence limits overlap. They did in a practice emap, june 2010 one, and it said use words like chance and probability, but I didnt have a clue what to write. An exact answer would be appreciated

[thegodofgod]

(Original post by Revd. Mike)
In an ideal world perhaps, but how often is that the case? In any sample, the statistics will never be as representative as they are for the whole population.

Fair enough, but then why 'n-1' specifically; why not some complicated log / e / ln *tries to think of complicated maths stuff* based formula, or is it 'n-1' at A level to keep it simple?