Edexcel S3 - Wednesday 25th May AM 2016

Spearman rank correlation coefficient, when ranking the values, if you rank biggest value of x, 1 and smallest 10, then you do the same for y even if it gives you a negative value which means a negative correlation?

Haha, no problem! I fully understand the independence thing now, thank you. If only the textbook was as clear as your description lol.

just run through my note on significant testing and i wrote " for PMCC, variables have to follow normal distribution", and i have no idea what this mean and how this applies ..........

Correct.

It just means that if you want to use the pmcc, you have to assume that "the data is distributed bivariately normal". No point understanding it at this point, just memorise it and write it in the exam if they ask you "what assumption did you make for pmcc?"

wow thank you, imagine if this question actually comes up tmr lol

Wouldn't be surprised, I just hope quota sampling doesn't come up.

I'm getting quite good at the sampling methods actually, my teacher trained us by making us do the bloody long aqa questions where i literally got 0/9 the first time i did it lol.
actually i realised that the question about primary and secondary data never came up before, the book specify that we need to know about it

What is a mean?

I remember primary/secondary **** from my business GCSE lol I'll be able to blag my way through.

lol I did so bad at Business Studies that i decided to give up my dream on being the second Bill Gate.
Anyway, thank you for your help today, im gonna sleep early, goodluck tmr !!

Putting it up here for you, hope you don't mind:

Really confused about something guys!!Uno when u use contingency tables for chi squared u do (row-1)(column-1) to get degrees of freedom- if you then pool/combine a row (frequencies<5) do u take 1 away from the value of v?I.e. (3-1)(2-1)-1?Thanks!!

Nope, then you work out v with the new number of rows and columns.

Oh so if one of the 'squares' of the table have frequencies<5, the entire column is merged with the one on the left?

A fair die is rolled 35 times. Find the approximate probability that the total of the 35 scores is less than 100.

For this how do you get the variance and mean

I know how to do the CLT part, just stuck on this - is it discrete uniform? how would I calculate the mean and var

Yeh dicrete uniform.
Mean is 3.5 by symmetry. Calculate E(X^2) by the sum of scores squred tkmes 1/6. Then varx=E(x^2)-((ex))^2



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