Functions and Transformations - Will it be on Exam P?

[sballen]

I'm taking exam P at the end of March and I'm having trouble with functions and transformations of random variables. I'm using the ACTEX study guide and it's section 9. My question is; how often do these come up on Exam P?

I've spent a lot of time trying to understand this and just can't comprehend them (I understand everything else leading up to this section). I'm debating whether I should skip section 9 and move onto section 10 and then the practice exams or if I should continue to spend time trying to understand this. Obviously my time is limited and I need to start taking practice exams ASAP.

Any input is greatly appreciated, thanks!

[bellaisa]

It's on the syllabus so There's a chance that it'll show. The transformation section leaves much to desire in the actex manual, but do a couple of problems focusing on it and you'll pick it up.

I understand it as, find the inverse first, figure out if it's 1-1, then see if it's easier to use the CDF approach or would it be easier to use the PDF formula.
But from my understanding, it's easier to use the formula if is 1-1, and CDF approach if it's not 1-1. Of course, im just speaking about single densities, not joint densities.

[Academic Actuary]

I would like to know if anyone who has taken the exam has had a question involving transforms with two variables where a Jacobian is necessary?

[sballen]

Thanks for the info Bellaisa.

I'm just trying to figure out if it's worth spending so much time trying to understand that section if I may not have a question involving this. And if it is on the exam and there will only be one or two questions then is it really worth it? I think for now I'm going to skip that section, move onto section 10 and then do a couple practice exams to see where I'm at.

[CALCULUS]

hey guys u gotta learn that stuff cos i met two pretty questions on my exam in 2011. the jacobian was useful in an exponential case since it was bivariate in nature.

[MathandBikes]

I had trouble with transformation questions when I first came upon them. I skipped it initially and then went back to it and I guess my mind had the time it needed for it to sink in. I suggest moving on but put it in a list of things that you'll need to review again while cranking out problems. Going back and reviewing the material you struggled with can be a nice break ocassionally while solving 100s of problems.

I also suggest becoming comfortable with both methods. I found using the PDF with the inverse and then using substitution with the derivative much easier at first but the CDF method is eventually what really helped me understand the underlying concepts.

[StudyingIsFun]

If you do get a transformation question it will have to be pretty easy to solve. A difficult transformation takes several minutes and this is not going to appear on the exam. If I were you I would focus on the CDF method approach and ignore the Jacobian if you do not have time. You will likely only need around 18/30 right to pass, so if you are pressed for time I would not worry about focusing on a difficult concept where you would get 1 or 2 questions on it at most.

If you study the topic well and average 1 question per exam on it and get it right 75% time you are only increasing your score by .55/30 over guessing. That's just under 2%. I would pass on it if you don't have the time.

[Actuary Maybe?]

I did not get any when I took P last year. However, you should feel comfortable solving it. It should be just simple calculations.

[sballen]

Thanks studyingisfun, great advice. Also thanks to everyone else who responded.

[kittens]

I had one transformation on my exam which was a pretty easy one