Edexcel S1 A Level Maths

i presume it would be, because the real values are still continuous, because if you get say for example 27 mins 52 seconds ..... and so on and you round it to the nearest minute of 28 mins, the actual value is still continuous

This is from Jan 2011 question 6 and I have no clue how question e and f, if anyone has any clue please help!

http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202011%20-%20QP/6683_01_que_20110114.pdf
6. The discrete random variable X has the probability distribution
x 1 2 3 4
P(X = x) k 2k 3k 4k
(a) Show that k = 0.1
(1)
Find
(b) E(X)
(2)
(c) E(X 2)
(2)
(d) Var(2 – 5 X )
(3)
Two independent observations X1 and X2 are made of X.
(e) Show that P(X1 + X2 = 4) = 0.1
(2)
(f) Complete the probability distribution table for X1 + X2
(2)
y 2 3 4 5 6 7 8
P(X1 + X2 = y) 0.01 0.04 0.10 0.25 0.24


___________________________________________________________________________
___________________________________________________________________________

that's what i thought although in this paper they seem to have treated it as discrete (it's question 4):
http://www.carlgauss.co.uk/PDFs/A-Level%20Papers/S1/S1%20-%202003%20Jan%20Paper.pdf

the markscheme shows them taking the 10.5th value, 4.5th value and 15.5th value for the quartiles. :s
http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/Maths/S1_January_2003_mark_scheme.pdf

maybe it's just an old paper? i'm really not sure.

Don't think too deeply into it. Continuous data, grouped frequency table. Discrete data, ungrouped data outside of a table.

So let me get this straight if you have data that like (2 5 9 1 8 11 90 72 85 81 51 39 etc) to find the median would I do N+1/2 or just N/2

So let me get this straight if you have data that like (2 5 9 1 8 11 90 72 85 81 51 39 etc) to find the median would I do N+1/2 or just N/2

When drawing the regression line do you plot anything else apart from the means? Have you guys done the Jan 2013 paper? Is it just me or was that paper quite tricky??

So let me get this straight if you have data that like (2 5 9 1 8 11 90 72 85 81 51 39 etc) to find the median would I do N+1/2 or just N/2

I think everyone hated that paper. I'm about to attempt it now. WISH ME LUCK

Aight, for statistical independence in probability questions like these remember two rules P(A|B)=P(A). P(B|A)=P(B) . P(A)P(B)=P(AnB)

So, we know from the previous question the probability of kamil being late given jake being late is 0.15/0.25 = 0.6. Now if we using the equation P(K|J)=P(K) we can see that if P(K|J)= 0.6 and P(K) = 0.2 that they are not equal therefore not independent. In part e the teacher has a suspicion if they are linked, independent means they are not related at all, so if kamil and jakes lateness is not independent they are somehow linked therefore confirming her suspicion

d) We have P(J) 0.25 and P(K) 0.2 which you calculated earlier in the question.

If P(J) * P(K) = P(J n K) it will be statistically independent

However, 0.25*0.2 = 0.05 =/= (P(J n K) so J and K are not independent

e) Confirms teachers suspicions since Jake and Kamil could be going to school together, since they are dependent.

Can anyone put a link for the Jan 2013 paper???

Hey Guys,

I have a few issues and queries:

First of all:

Can someone explain to me how skewness works and every possible way of working out the skewness?

How do you relate it back to the data, for example I have no difficulty working it out and stating whther it's postively skewed, negatively skewed or symmetrical. But is that enough or would I have to relate it back to the data.

When is it best to use the mean and median?

I understadn when they are two completely different numbers and you apply it to the context for example at a sale you'd pick the lower one, but what if they don't give you much context and they ask which is the best.

All I know is that you'd wouldn't pick mean if there are outliers as extreme values affect the mean

When would you not pick the the median? Are there any other reasons not to pick the mean?

When finding the median using interpolation when should you take the upper and lower bound?

Which is right:

x f CF
0 - 100 3 3
100 - 200 4 7
200 - 300 3 10


0 m 100
-------------------------------
3 5 7 and then use a/b = c/d


x f CF
0 - 99 3 3
100 - 199 4 7
299 - 300 3 10


99.5 Q3 199.5
----------------------------------------
7 7.5 10 then use a/b - c/d

How does coding work?

Coding does not affect pmcc, but addition/subtraction and multiplication/division affects the mean

but Standard deviation is only affected by division/subtraction.

mean of v = 45 and the SD = 15 n = 9 and v = (x-5)/10

would the uncoded mean be:
45*9 = 405
405 - (9*5)/10 = 36


or would it be:

45 - 5/10 = 4

For the uncoded SD would it be:

15/10 = 1.5

Thanks I've got so many Qs, so anyone willing to help I'd be really grateful.

A group of office workers were questioned for a health magazine and 2/5 were found to take regular exercise. when questioned about their eating habits 2/3 said they always eat breakfast, of those who always eat breakfast 9/25 also take regular exercise

find probability randomly selected member
a) always eat breakfast and take regular exercise
b) does not eat breakfast and not take regular exercise
c) determine, weather or not always eating breakfast and taking regular exercise are statistically independent
understand a, not b could someone help please??