VCE Methods Question Thread!

[TheCommando]

It is using the rule

**Bring the power to the front and reduce the power by 1**
However the inside of the function is not x so I must also take that into account by using the chain rule hence why I multiply by the derivitive of the inside.
Remember the chain rule is basically derivitive of outside multiplied by the derivitive of the inside.

Ohhhh righht! Thank you!!!

[Willba99]

This is what the derivitive looks like. When integrating you will get something with inverse tans and square roots.

Sorry I meant anti-derive.
I tried using partial fractions so i can antiderive easily and i cant seem to separate them right. I keep getting 1/2sqrt(a) as both my A and B values, but when i graph the partial fraction function compared to the original one (using arbitrary values for a and b) they aren't the same. Could you have a look at my working out? I attached it as a picture.

[Shadowxo]

Sorry I meant anti-derive.
I tried using partial fractions so i can antiderive easily and i cant seem to separate them right. I keep getting 1/2sqrt(a) as both my A and B values, but when i graph the partial fraction function compared to the original one (using arbitrary values for a and b) they aren't the same. Could you have a look at my working out? I attached it as a picture.

Has been answered here.
Note: please only post once, in the relevant forum

[Lavar Big BBB Balls]

Hi

I need help on these 2 Qs http://imgur.com/a/v8LlO

Q3) How is the answer not B? My teacher seems to have taught me to think of a confidence interval as what B suggests and google's definition of a confidence interval agrees.

The correct answer is D, but answer acknowledges that B is a common misconception of a C.I

Q8) Not directly related but I got this wrong by choosing D. I'm getting confused because in spesh, the population mean is equal to the mean of the sample mean. Is there an equivalent scenario in methods where the population proportion is equal to the sample proportion?

[VanillaRice]

Hi

I need help on these 2 Qs http://imgur.com/a/v8LlO

Q3) How is the answer not B? My teacher seems to have taught me to think of a confidence interval as what B suggests and google's definition of a confidence interval agrees.

The correct answer is D, but answer acknowledges that B is a common misconception of a C.I

Q8) Not directly related but I got this wrong by choosing D. I'm getting confused because in spesh, the population mean is equal to the mean of the sample mean. Is there an equivalent scenario in methods where the population proportion is equal to the sample proportion?

3) I would argue that D is the 'better answer', since it makes mention of the random samples being used to calculate the CIs. I guess it's worth noting that sometimes, you'll often find that definitions and agreements among statisticians will often vary. This is most likely not a typical question that would come up in an exam, but if you'd like clarification - the best source of information is the relevant section in the textbook (since the authors are most likely the ones who wrote the question.

8 ) A point estimate is a sample statistic that we use to estimate a population parameter (i.e. point estimate cannot be the population parameter). If we knew the population proportion, there's no point in estimating it! 
I'm not quite sure what you mean by the population mean is equal to the sample mean, would you able to elaborate on this?

Hope this helps

[Lavar Big BBB Balls]

3) I would argue that D is the 'better answer', since it makes mention of the random samples being used to calculate the CIs. I guess it's worth noting that sometimes, you'll often find that definitions and agreements among statisticians will often vary. This is most likely not a typical question that would come up in an exam, but if you'd like clarification - the best source of information is the relevant section in the textbook (since the authors are most likely the ones who wrote the question.

8 ) A point estimate is a sample statistic that we use to estimate a population parameter (i.e. point estimate cannot be the population parameter). If we knew the population proportion, there's no point in estimating it! 
I'm not quite sure what you mean by the population mean is equal to the sample mean, would you able to elaborate on this?

Hope this helps

Thanks.

I meant for Q8) in spesh the population mean is always equal to the mean of the sample mean. I was wondering if methods has something equivalent but with population proportions and sample proportions?

[VanillaRice]

Thanks.

I meant for Q8) in spesh the population mean is always equal to the mean of the sample mean. I was wondering if methods has something equivalent but with population proportions and sample proportions?

It seems plausible to think that the mean of the sample proportions would be approximately equal to the population proportion. Whether or not this covered in Methods though I'm not sure of (hopefully someone else can answer this though).

[Sine]

Thanks.

I meant for Q8) in spesh the population mean is always equal to the mean of the sample mean. I was wondering if methods has something equivalent but with population proportions and sample proportions?

Well on the formula sheet is says E(p^) = p which is the expected value/average of the sample proputions is equal to the population proportion. Not 100% sure if this is what you were after. 

I have attatched a snippet from the formula sheet.

[Lavar Big BBB Balls]

Well on the formula sheet is says E(p^) = p which is the expected value/average of the sample proputions is equal to the population proportion. Not 100% sure if this is what you were after. 

I have attatched a snippet from the formula sheet.

Thanks, yeah that was what I was looking for.

If that is the case, in my question about Q8, couldn't you then argue that A is a possible answer? Since E(p^) = centre of confidence interval = p which is a population parameter?

[TheCommando]

https://m.imgur.com/a/1HFnt
For questionn 12, why do u do (6/10)^3 instead of (4/10)^3
Does the replaced mean whatt eve ris ttaken out is put back in as well

Also for q15 why do i add the numbers

[TheCommando]

https://m.imgur.com/a/1HFnt
Hey, how do i do q16 b annd 17a

[Shadowxo]

https://m.imgur.com/a/1HFnt
For questionn 12, why do u do (6/10)^3 instead of (4/10)^3
Does the replaced mean whatt eve ris ttaken out is put back in as well

Also for q15 why do i add the numbers

12. If you're finding the probability you don't pick a black ball 3 times (ie you get 0 black balls), it's (6/10)³ ie probability you pick a red ball every time. If you're finding the probability you get 3/3 black balls, it would be (4/10)³. If it's replaced that means you put it back in after you take it out. Not replaced means it's taken out and not put in, therefore decreasing the total number of balls by 1 each time

15. It is a bit ambiguous, it didn't say the sum of the numbers was noted. In the exam they would be more specific though, so don't worry

PS you didn't link Q16 and 17. What exactly got you stuck though?

[VanillaRice]

Thanks, yeah that was what I was looking for.

If that is the case, in my question about Q8, couldn't you then argue that A is a possible answer? Since E(p^) = centre of confidence interval = p which is a population parameter?

When you calculate a CI for the sample proportion, you are using the sample proportion plus or minus the margin of error. Therefore, the sample proportion, p hat, is the centre of the confidence interval. The sample proportion is not (always) equal to the population proportion. I think that you've got this mixed up with the expected value of the sample proportion being equal to the population proportion.

Hope this clarifies things

[A TART]

https://m.imgur.com/a/1HFnt
Hey, how do i do q16 b annd 17a

The link wasn't supplied so I assume it was from the same chapter? Here's my solution (CORRECT me if im wrong. I haven't done unit 3/4 yet.)
https://imgur.com/a/q6GFJ


PS: When you are told to graph a full cycle (for a circular function), that means you graph an entire period right? (not 360 or 2pi right? Coz that's what i assume a cycle is when i visualise it)

[Shadowxo]

The link wasn't supplied so I assume it was from the same chapter? Here's my solution (CORRECT me if im wrong. I haven't done unit 3/4 yet.)
https://imgur.com/a/q6GFJ


PS: When you are told to graph a full cycle (for a circular function), that means you graph an entire period right? (not 360 or 2pi right? Coz that's what i assume a cycle is when i visualise it)

Yes, a full cycle is the entire period
Don't worry about the following if you don't understand it: You're essentially graphing from cos/sin(0) to cos/sin(2pi) ie going around the circle once, but different x values result in different values inside the brackets, eg for cos(x/2), x=2π results in cos(2π/2)=cos(π) which is only half a cycle, so you have to graph from x=0 until x=4π which would result in cos(2π), a full cycle