VCE Methods Question Thread!

[Syndicate]

To make it easier, you might want to make the probability distribution in terms of X-1. So the top row would change to values -1, 1, 2 and 4, whilst the probability values would remain the same.

[TheCommando]

Hey, i have no idea on how to do d e and f
https://imgur.com/a/dJsnE

[Rieko Ioane]

Hi, have some small questions

https://imgur.com/a/N9m6k
Q4a) can someone confirm for me that domain: R\[-1/2,1/2] is correct here?

Q15) Is it appropriate to use the normal approximation here even if it is not asked?
The question did it regardless and got an answer of 0.02. I did it binomially and got 0.016 but had to round it by a lot - it still ended with D.

Thanks

[VanillaRice]

Hey, i have no idea on how to do d e and f
https://imgur.com/a/dJsnE

Hey there, I can't seem to see any images (it might just be my computer). Could you double check?

Hi, have some small questions

https://imgur.com/a/N9m6k
Q4a) can someone confirm for me that domain: R\[-1/2,1/2] is correct here?

Q15) Is it appropriate to use the normal approximation here even if it is not asked?
The question did it regardless and got an answer of 0.02. I did it binomially and got 0.016 but had to round it by a lot - it still ended with D.

Thanks

4a) Looks fine to me I'm assuming you got your answer by restricting the domain such that Ran g = R⁺?

15) It's called an approximation because it is indeed that. In other words, your answers using both methods will be similar (assuming a large enough sample size). One issue you might face is having to decide between options A and B. If the answers were relatively distinct (i.e. not too close to each other), I guess using either method would be fine, but, if this was a short answer question, definitely do it the way the question intends.

Hope this helps

[gnaf]

Hey

How do you do Q21 of 2015 Exam 2 VCAA? Stuck btwn C and D (I got to m^2+4ac<0)

And for Q22, how is g(x)=tan(x) as the examiners report says? It's not symmetrical?

[Shadowxo]

Hey

How do you do Q21 of 2015 Exam 2 VCAA? Stuck btwn C and D (I got to m^2+4ac<0)

And for Q22, how is g(x)=tan(x) as the examiners report says? It's not symmetrical?

For 21 you simply have to solve the equation you found  (m²+4ac<0)

Which corresponds to D

22. They just chose functions that look similar to the displayed ones. Also I believe |x| (modulus graphs) aren't in the methods study design anymore.
For -f(x),  -f(x)=-f(-x) so the graph is symmetrical (even function) and is non-negative for all values of x. So for g(-f(x)), its also symmetrical, as -f(x) is even / symmetrical. And since -f(x) is positive and a straight line starting from 0, you can essentially just take the right hand side of the graph g(x) ie where x>0 and make it symmetrical.
Since -f(x) is just like x for positive x values, g(-f(x)) is just like the right hand side for the graph, and since -f(-x)=-f(x), it's symmetrical.
Sorry for the long and confusing explanation, but hope this makes a bit of sense

[geminii]

Hey everyone,

I'm trying to figure out the following binomial probability problem:

Suppose that X is the number of offspring that survive their first year in a wolf litter. The probability that a wolf survives its first year is 0.3, and the average litter is 6 puppies.
a) Write a rule for the probability distribution for the number of pups in an average litter that survive their first year.
I did Pr(X=x) = (6) * (0.3)^x * (0.7)^(6-x)
                        (x)

But I am not sure whether n should be 6 or 7. I wrote 6 because there are six pups in a litter, but should it be 7 since there is a probability that 0 survive? I don't know, I am really confused, any and all help is appreciated!!

[LifeisaConstantStruggle]

There should be 7 values yeah. But the values are 0,1,2,3,4,5,6 so n should still be 6

[Shadowxo]

Hey everyone,

I'm trying to figure out the following binomial probability problem:

Suppose that X is the number of offspring that survive their first year in a wolf litter. The probability that a wolf survives its first year is 0.3, and the average litter is 6 puppies.
a) Write a rule for the probability distribution for the number of pups in an average litter that survive their first year.
I did Pr(X=x) = (6) * (0.3)^x * (0.7)^(6-x)
                        (x)

But I am not sure whether n should be 6 or 7. I wrote 6 because there are six pups in a litter, but should it be 7 since there is a probability that 0 survive? I don't know, I am really confused, any and all help is appreciated!!

Yes there are 7 possible outcomes / x values, but since there are 6 pups, n=6 (it's like you're repeating it 6 times).
So n=6 and x can be between 0 and 6.
Just remember n is the number of trials, so in this situation you're doing a trial for each pup, ie 6 times

[GloriousHeights]

Hi! I have a probability question, but I don't have the exact question.
How would I find the upper and lower bounds of a question like this:
Pr(a<Z<d)=0.95
Thank you 

[Rieko Ioane]

https://imgur.com/a/8EJrC

For the question above, is the best way to do this by drawing the graph that I have drawn?

Is there any method that would solve for the coefficients?

Thanks.

[GloriousHeights]

I'm not sure what the best way to solve it is 

[Eric11267]

Hi! I have a probability question, but I don't have the exact question.
How would I find the upper and lower bounds of a question like this:
Pr(a<Z<d)=0.95
Thank you 

The question could have multiple solutions since a and d can take on a number of different values.
If you mean Pr(-a<Z<a)=0.95 then you would do Pr(Z<-a)=0.025 using the symmetry properties of the normal curve
Using the inverse normal function on a graphics calculator can then get you the value of -a.

[Eric11267]

https://imgur.com/a/8EJrC

For the question above, is the best way to do this by drawing the graph that I have drawn?

Is there any method that would solve for the coefficients?

Thanks.

I'd say that graphing it is the best way. If you wanted to find coefficients, it would involve at least 5 different equations, which would be a hassle for a multi choice question.

[gnaf]

what's the domain of the inverse of loge(1-x^2)?

The ans says (-infinity, 0] but I got [0, loge20)?