Year 12s: what will be the first way you research your future options? >>

Edexcel S3 - Wednesday 25th May AM 2016

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Reply 780

kennz

Original post by tazza ma razza

read through the thread, i asked this about 2 hrs ago.

you apply sxy and sxx etc using the ranks not the actual data

cheers, thats what i thought.

Reply 781

tazza ma razza

Does anybody have the paper asking to test if normal distrubtion is a suitable distrubtion?

Reply 782

tazza ma razza

when doing ch 5 stuff - pmcc and srcc - do you use the ρ in both cases when writing H0 and H1?

(edited 7 years ago)

Reply 783

coolguy123456

Original post by tazza ma razza

read through the thread, i asked this about 2 hrs ago.

you apply sxy and sxx etc using the ranks not the actual data

I haven't seen a question like this, have you come across one where they've used ranks to calculate PMCC? Textbook and past paper questions only use the data itself to calculate PMCC.

Reply 784

username1162972

Original post by tazza ma razza

when doing ch 5 stuff - pmcc and srcc - do you use the ρ in both cases?

Yeh think so.

Posted from TSR Mobile

Reply 785

tazza ma razza

Original post by physicsmaths

Yeh think so.

Posted from TSR Mobile

as in the hypothesis writing?????

(edited 7 years ago)

Reply 786

tazza ma razza

Original post by coolguy123456

I haven't seen a question like this, have you come across one where they've used ranks to calculate PMCC? Textbook and past paper questions only use the data itself to calculate PMCC.

Yh, but then ranking would be pointless wouldn't it. Ie you would go straight to the pmcc without ranking.

Reply 787

Ayman!

Original post by tazza ma razza

Yh, but then ranking would be pointless wouldn't it. Ie you would go straight to the pmcc without ranking.

Okay, now I'm confused. Once we have a tie, we average the ranks and calculate the PMCC using only the ranks?

Reply 788

coolguy123456

Original post by tazza ma razza

Yh, but then ranking would be pointless wouldn't it. Ie you would go straight to the pmcc without ranking.

So if they've given data which they've asked to calculate SPCC and then part b for example says 2 ranks are now tied, use PMCC, would we calculate Sxx, Syy, Sxy using the ranks (including the now tied rank)?

Reply 789

justalawyer1998

Really cba to go back to S1 and S2 after this

Reply 790

tazza ma razza

Original post by Nikhilm

Really cba to go back to S1 and S2 after this

i got s4 after this :smile:

Reply 791

paradoxequation

Original post by kennz

If you are calculating spearmans rank and two units have the same rank, you take an average of that rank and the next and then use PMCC. How would you use PMCC if the data is ranked/ordinal?

What do you mean by "take an average of that rank and the next"?

Reply 792

tazza ma razza

Original post by coolguy123456

yes

eg sxx = sum of x^2 - (sum of x)^2 /n , where x is the rank, not the data

then multiply the 2 ranks as per for sxy

(edited 7 years ago)

Reply 793

username1162972

Original post by tazza ma razza

Yh, but then ranking would be pointless wouldn't it. Ie you would go straight to the pmcc without ranking.

ranking it and using spearman is quick but less accurate. i thought you do the pmcc u just calculate it from raw data, i might be wrong since im **** at stats.

Reply 794

connorbarr

Original post by Zacken

Yep, but I doubt the case will arise.

has come up on a past paper i remember, asked you why the degrees of freedom was this value and it was a contingency table, had to combine some frequencies cos one was less than 5

Reply 795

Zacken

Original post by connorbarr

has come up on a past paper i remember, asked you why the degrees of freedom was this value and it was a contingency table, had to combine some frequencies cos one was less than 5

Yes, June 15. You had to explain why, but you didn't actually have to combine it yourself which was what I was talking about.

Reply 796

tazza ma razza

Original post by connorbarr

has come up on a past paper i remember, asked you why the degrees of freedom was this value and it was a contingency table, had to combine some frequencies cos one was less than 5