How was Mathematics Paper 72 (Statistics 2)?

[Keirad]

Q3
E(X) was 150, Var (X) was 30,000 (I accidentally wrote the s.d. tho )
In the last q I'm afraid you had to divide P(X<4) by P(X>=1) :S

I got the same answer for Q3 but for the conditional probability i did what shrz09 said

 

[shrz09]

I just realised you're probably right.

Yet the diference is very small in our workings,not more than 1 mark will be lost by whoever among us did it wrong,lets see

 

[Abdo332]

What do you guys say the GT will be? I say It'll be lower this time..a 40.

 

[randomcod]

What do you guys say the GT will be? I say It'll be lower this time..a 40.

My guess is 37, as it had 2 tricky qs and that is the gt papers with tricky qs get
Bear in mind this is xtremepapers so this will be a terrible sample to know the overall GT as obviously users on xtremepapers are more 'keen', if that makes sense.

 

[randomcod]

Yet the diference is very small in our workings,not more than 1 mark will be lost by whoever among us did it wrong,lets see

Thanks for the encouragement, bro I really hope you're right

 

[guccifier]

I also got E(x) 150 and Var(x) 30000, as far as q5 is considered it was regarding confidence intervals,part 3 was (0.96)^4 as per binomial process.While as per my concepts the conditional probability was not p(x<4)/p(x is greater or equal to 1).Rather it was p(x=1,2,3)/p(x is greater or equal to 1) as zero is not an intersection between p(x is greater or equal to 1) and p(x<4)

yep, exactly what I did for both questions

 

[randomcod]

So what do you guys think the OVERALL Grade Threshold will be this year for an A* in maths? Assuming you did P 12 and 62 last year, and 32 and 72 this year

 

[Willi123]

How can you get 30,000 as variance? That makes the mean 150, and standard deviation 173.2 (if variance = 30,000). Do you really think the standard deviation can be greater than the mean? Think again.

 

[randomcod]

How can you get 30,000 as variance? That makes the mean 150, and standard deviation 173.2 (if variance = 30,000). Do you really think the standard deviation can be greater than the mean? Think again.

Of course it can
Google it
Think again

 

[Willi123]

I don't recall getting any standard deviation in S2 that was greater than the mean. But oh well, we'll have to wait till the marking scheme is out to decide that.

 

[guccifier]

Yes it is possible, you can get a variance greater than mean, but you can't get a sd greater than the mean

 

[randomcod]

Yes it is possible, you can get a variance greater than mean, but you can't get a sd greater than the mean

You can
I don't know where you people get this info from ¬¬