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

Reply 180

KloppOClock

14

whats the formula for standard deviation? i googled it and like 50 different variations came up

Reply 181

aj2152

2

Original post by KloppOClock

whats the formula for standard deviation? i googled it and like 50 different variations came up

ImageUploadedByStudent Room1465652854.026067.jpg

This is the most used formula, but the formula for V and SD is slightly different when you are working with Discrete Random Variables/Normal Distribution. Check the Edexcel S1 summary page at the end of each chapter to be sure.

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Reply 182

KloppOClock

14

I dont get question 4 part d
https://1a388b28f5ce9318f837a64962fc3ceab9c61da8.googledrive.com/host/0B1ZiqBksUHNYU2s1SVY1VDN2Q0U/January%202010%20QP%20-%20S1%20Edexcel.pdf

Question is what is the probability of some studying SnDnN given that they study SnN.

So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

which = (4/180) / (36/180) = 1/9

however the answer says its 1/10

Reply 183

4nonymous

11

Original post by KloppOClock

I dont get question 4 part d
https://1a388b28f5ce9318f837a64962fc3ceab9c61da8.googledrive.com/host/0B1ZiqBksUHNYU2s1SVY1VDN2Q0U/January%202010%20QP%20-%20S1%20Edexcel.pdf

Question is what is the probability of some studying SnDnN given that they study SnN.

So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

which = (4/180) / (36/180) = 1/9

however the answer says its 1/10

There are 40 people who do SnN and of those 40, 4 do all three, so its 4/40=1/10

Reply 184

KloppOClock

14

Original post by 4nonymous

There are 40 people who do SnN and of those 40, 4 do all three, so its 4/40=1/10

but why isnt it conditional

Reply 185

4nonymous

11

Original post by KloppOClock

but why isnt it conditional

Have a look on exam solutions he explains how to work it out.

Reply 186

KloppOClock

14

Original post by 4nonymous

Have a look on exam solutions he explains how to work it out.

i did he just briefly said what the other guy above said

Reply 187

Maetras

9

Original post by Philip-flop

Well you already know that the question is asking what the probability of her phone lasting 133 hours is. Think about it this way....

P(not need charging after 133 hours)
= P(L>133 | L>127)
= _P(L>133)_
P(L>127)

^It's probability after 133 hours because why would she want to charge her phone before her flight is over!

Hope this helps :smile:

Yeah thanks that helped a lot :smile:

Reply 188

username2596081

9

when you go to find the sum of x^2, sum of y^2, sum of xy etc. would you get penalised for doing it using your calculator. What I mean is, would you get penalised for not working out the squares of every x and adding them up, because i feel that its easier and quicker to just stick your data into your calc on stat mode, and work it out that way

Reply 189

physicsamor

20

Original post by ishaniss

when you go to find the sum of x^2, sum of y^2, sum of xy etc. would you get penalised for doing it using your calculator. What I mean is, would you get penalised for not working out the squares of every x and adding them up, because i feel that its easier and quicker to just stick your data into your calc on stat mode, and work it out that way

Well its always useful to show your method, look at the mark schemes and see if marks are awarded for methods or just answers

Reply 190

apparently_anerd

What's the difference between being not independent and mutually exclusive?

Reply 191

physicsamor

20

Original post by KloppOClock

I dont get question 4 part d
https://1a388b28f5ce9318f837a64962fc3ceab9c61da8.googledrive.com/host/0B1ZiqBksUHNYU2s1SVY1VDN2Q0U/January%202010%20QP%20-%20S1%20Edexcel.pdf

Question is what is the probability of some studying SnDnN given that they study SnN.

So that is P(SnDnN | SnN) which = P(SnDnN n SnN) / P(SnN)

which = (4/180) / (36/180) = 1/9

however the answer says its 1/10

You've calculated wrong probably due to the venn diagram misleading you

Remember there is 40 people do S&N not 36

So P (S&N&D/ S&N) = 4/40

Reply 192

KloppOClock

14

Original post by physicsamor

You've calculated wrong probably due to the venn diagram misleading you

Remember there is 40 people do S&N not 36

So P (S&N&D/ S&N) = 4/40

thank you! :smile:

Reply 193

physicsamor

20

Original post by KloppOClock

thank you! :smile:

No problem, I made the same mistake and I just had to read through it a few times because no solutions were helping me :h:

Reply 194

apparently_anerd

Hi, I was wondering if anyone could answer a few questions I had:

1. What sorts of things might we be asked about statistical models and what do we need to know?

2. What functions of the fx-991ES PLUS calculator can we use in the exam

3. What's the difference between mutually exclusive events and independent events or is there non?

Reply 195

Aliceeee12

2

Original post by apparently_anerd

Hi, I was wondering if anyone could answer a few questions I had:

1. What sorts of things might we be asked about statistical models and what do we need to know?

2. What functions of the fx-991ES PLUS calculator can we use in the exam

3. What's the difference between mutually exclusive events and independent events or is there non?

1. advaantages and disadvantages i have seen in past pprs
3. MEE p( a and b) = 0
Independant: p(a and b) = p(A) times p(B)

Reply 196

4nonymous

11

Original post by apparently_anerd

Hi, I was wondering if anyone could answer a few questions I had:

1. What sorts of things might we be asked about statistical models and what do we need to know?

2. What functions of the fx-991ES PLUS calculator can we use in the exam

3. What's the difference between mutually exclusive events and independent events or is there non?

someones already answered 1 and 3 so:

2. There are a lot of things you can do on your calculator. You can work out:
mean
variance
standard deviation
sum x^2, sum y^2 etc
Normal distribution

Reply 197

KloppOClock

14