VCE Methods Question Thread!

[keltingmeith]

Thanks so so much EulerFan101 

so if we are given a PDF where  one part of the graph is not  included for a particular interval.(like this example)
Does that mean the elsewhere part of the graph will be included?

Like for this example at x=0  we know that x=/=0 for the e^{-x} part.(not included-open circle)

so  does that mean x=0 will be included in the elsewhere part of the graph ?(closed circle)

Yes, that is exactly it. As I said, like with any other hybrid function.

[knightrider]

Yes, that is exactly it. As I said, like with any other hybrid function.

Thanks for clarification EulerFan101 

just wanted to ask you something.

When you did methods what do you reckon was the best things to do in terms of exam prep.
Also how did you go about learning the concepts?

Thanks 

[keltingmeith]

Thanks for clarification EulerFan101 

just wanted to ask you something.

When you did methods what do you reckon was the best things to do in terms of exam prep.
Also how did you go about learning the concepts?

Thanks 

Oh God, so long ago... (I mean, 2 years, but I can't actually remember waking up, so...) I will stress that this is what worked for me - that doesn't mean it'll work for you. Furthermore, I took a very "different" approach to VCE, so keep that in mind.


The way I did it, was I didn't try to sit in one place for too long. Once I learned something, when it came to doing practice problems, I didn't do the "assigned" questions. Instead, I'd do the first few, and once it was clear I knew what I was doing, I moved right on. Sometimes, this meant that I did one question in a whole exercise - I figured there was no point in beating a dead horse. This also meant I got to move on from the skills questions (eg, those questions on diffing circs just so that you know you can, even though it's not something that'll be assessed by itself), and very quickly into exam stuff. Didn't have to learn ahead, either - because I didn't spend so long on those skills questions, I had heaps of time to do exam stuff.

As for exams, I only ever looked at exam 1s (I DO NOT SUGGEST THIS IN THE SLIGHTEST NOW, THOUGH - ONLY DOING EXAM 1s IS A BAD IDEA FOR SEVERAL REASONS. You should also *at least* do the multiple choice section of exam 2s). I made sure I could do every question - and once I did the exam, I looked over it again. This was probably the best part of my exam prep - after I did a question, if I ever thought there was a second way of doing it, I would do the question again.

I know it's very easy to ask people "why did you use technique x for this question, instead of technique y?" and get a detailed answer, so I avoided this as much as possible. If I thought I could use y instead of x, I tried it out myself, and saw where it got me. Often, this meant hitting a dead-end, and I learned why technique y would never work. Sometimes, though, this meant finding an answer much more quickly. This is why I would go over the exams a second time - because a few times, I'd get a new technique out of it. If I didn't get a new technique, I knew what to not do any longer.

[knightrider]

Oh God, so long ago... (I mean, 2 years, but I can't actually remember waking up, so...) I will stress that this is what worked for me - that doesn't mean it'll work for you. Furthermore, I took a very "different" approach to VCE, so keep that in mind.


The way I did it, was I didn't try to sit in one place for too long. Once I learned something, when it came to doing practice problems, I didn't do the "assigned" questions. Instead, I'd do the first few, and once it was clear I knew what I was doing, I moved right on. Sometimes, this meant that I did one question in a whole exercise - I figured there was no point in beating a dead horse. This also meant I got to move on from the skills questions (eg, those questions on diffing circs just so that you know you can, even though it's not something that'll be assessed by itself), and very quickly into exam stuff. Didn't have to learn ahead, either - because I didn't spend so long on those skills questions, I had heaps of time to do exam stuff.

As for exams, I only ever looked at exam 1s (I DO NOT SUGGEST THIS IN THE SLIGHTEST NOW, THOUGH - ONLY DOING EXAM 1s IS A BAD IDEA FOR SEVERAL REASONS. You should also *at least* do the multiple choice section of exam 2s). I made sure I could do every question - and once I did the exam, I looked over it again. This was probably the best part of my exam prep - after I did a question, if I ever thought there was a second way of doing it, I would do the question again.

I know it's very easy to ask people "why did you use technique x for this question, instead of technique y?" and get a detailed answer, so I avoided this as much as possible. If I thought I could use y instead of x, I tried it out myself, and saw where it got me. Often, this meant hitting a dead-end, and I learned why technique y would never work. Sometimes, though, this meant finding an answer much more quickly. This is why I would go over the exams a second time - because a few times, I'd get a new technique out of it. If I didn't get a new technique, I knew what to not do any longer.

WOW! Thanks for your insight  EulerFan101 

[knightrider]

For this question and working out attached.

When finding the median.

Why did they not use the negative root at this stage.

[keltingmeith]

For this question and working out attached.

When finding the median.

Why did they not use the negative root at this stage. (Image removed from quote.)

Remember that the mean, median and mode always (*always*) correspond to a possible x-value of the random variable. Can this random variable ever be negative?

[knightrider]

Remember that the mean, median and mode always (*always*) correspond to a possible x-value of the random variable. Can this random variable ever be negative?

The random variable  can never be negative.
But the values( possible x-values) of the random variable can be negative right?

but in this case the median is for the Pdf so it cant be negative right?

if it was for the values the PDF can take on then it could possibly be negative?

[keltingmeith]

The random variable  can never be negative.
But the values( possible x-values) of the random variable can be negative right?

but in this case the median is for the Pdf so it cant be negative right?

if it was for the values the PDF can take on then it could possibly be negative?

No - you're confusing what the pdf is and what values a random variable takes on.

The pdf is a description of the probabilities of the random variable - not what values the random variable takes on. For example, consider f(x)=e^x,x<0. In this case, the random variable takes on strictly negative values - but the pdf is strictly positive (as it *always* will be).

The values that the random variable itself takes on are the x-values - the domain of your pdf.

[knightrider]

No - you're confusing what the pdf is and what values a random variable takes on.

The pdf is a description of the probabilities of the random variable - not what values the random variable takes on. For example, consider f(x)=e^x,x<0. In this case, the random variable takes on strictly negative values - but the pdf is strictly positive (as it *always* will be).

The values that the random variable itself takes on are the x-values - the domain of your pdf.

Thanks EulerFan101 

[knightrider]

For this question attached.

is the reason they chose m=2.15554 instead of m=0.186682 because of the domain of the     graph?

[StupidProdigy]

How would you do this and get an exact value answer? The solutions just approximated...

find the real values of h for which f(x+h)=0 has two positive solutions, where f(x)=e^x-x^3+1
Thanks 

[keltingmeith]

For this question attached.

is the reason they chose m=2.15554 instead of m=0.186682 because of the domain of the  (Image removed from quote.)   graph?

See my last batch of advice.

How would you do this and get an exact value answer? The solutions just approximated...

find the real values of h for which f(x+h)=0 has two positive solutions, where f(x)=e^x-x^3+1
Thanks 

You cannot solve this analytically (that is, with exact values)

[Jay.C]

Hey guys! Just wondering if you could talk me through how to simplify the equations on the attached document.

Thanks! 

[knightrider]

See my last batch of advice.

Thanks EulerFan101 

Say if it was a 1 mark question and you have to give a reason why they chose that particular value of m.
What would you say?

[knightrider]

What influences if a distribution is symmetrical out of these and how?

Median or Mode or Mean