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  #101  
Old 10-15-2019, 08:00 PM
LilSam88 LilSam88 is offline
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Originally Posted by ThereIsNoSpoon View Post
Gonna register today. Is 2 months enough?
I hope so. I'm doing LTAM next week, taking a week off then and starting PA on first week of November. I will have 6 weeks to go through.
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  #102  
Old 10-19-2019, 04:21 PM
Zinger Zinger is offline
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Originally Posted by TinyTim7 View Post
A coworker of mine forwarded me an email with the plan below (from someone who passed PA recently). I will probably follow this plan, except I may go back and forth between the 3 parts, doing them kind of simultaneously.

1. Read chapters 1-6, 8 and 10 of Introduction to Statistical Learning (there’s a free PDF copy online here: http://faculty.marshall.usc.edu/gare...20Printing.pdf). You don’t need to do the lab sections at the end of each chapter because they mostly use different R commands than what you’ll see in the modules and exam. I actually really liked this book and it gives you a really good framework of the theory behind what you’re doing in the exam. I imagine a lot of the earlier chapters will already be familiar to you if you’ve done any linear regression stuff back in your experience studies days.

2. Take this online R course: https://www.udemy.com/course/data-sc...otcamp-with-r/ Looks like it’s on sale for $10 right now. Not all the sections are relevant but sections 1-23, 26-27 and 30-31 cover most of what you need to know in R for the exam (with a few exceptions like principal component analysis and ridge and lasso regression). It takes a while to get through the videos but if you watch them and follow along in R then it really does teach you the basics of how R works.

3. Work through the modules. A decent amount of the modules is stuff you can click through pretty quickly. Assuming they don’t change the content of the modules for the next sitting then I would say modules 1-5 are fairly introductory and straightforward, mostly about data design and plotting data in R (which you should know about already if you did step 2). The meat of the modules is in 6-8. Module 9 is a boring common sense module about how to write a report, which you don’t even need to do (except for an executive summary) under the new exam format anyway.
How did you get it for $10. It says on the website $194.99. Is there a coupon that we should be using to get it for $10? Let me know...
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  #103  
Old 10-21-2019, 10:31 AM
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TinyTim7 TinyTim7 is offline
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How did you get it for $10. It says on the website $194.99. Is there a coupon that we should be using to get it for $10? Let me know...
I think it is a first-time user discount. When I go on the website without being logged in, most of the courses are showing as around $200 with a slash through it, and the price reduced to $11.39
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  #104  
Old 10-21-2019, 11:29 PM
Zinger Zinger is offline
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It wasn't discounted for me earlier. Now it says $11.39 until Oct 24th .
Thanks!
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  #105  
Old 10-22-2019, 07:34 PM
SunnyDale SunnyDale is offline
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Default Ridge regression vs. lasso

I am having hard time understanding the one important difference between ridge regression and lasso:

the lasso has the effect of forcing the coefficient estimates to be exactly zero, however, for ridge regression the coefficient estimates are reduced but none are reduced to exactly zero

(taken from the ACTEX Manual)

why is this? I understand both would be non-negative since one is sum of squared X's and one is sum of absolute values, but why can't the sum of squared X's be zero?

Thanks!
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  #106  
Old 10-23-2019, 02:58 AM
ambroselo ambroselo is offline
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Originally Posted by SunnyDale View Post
I am having hard time understanding the one important difference between ridge regression and lasso:

the lasso has the effect of forcing the coefficient estimates to be exactly zero, however, for ridge regression the coefficient estimates are reduced but none are reduced to exactly zero

(taken from the ACTEX Manual)

why is this? I understand both would be non-negative since one is sum of squared X's and one is sum of absolute values, but why can't the sum of squared X's be zero?

Thanks!
To clarify, the regularization penalty term of both ridge regression and the lasso is in terms of the beta's, not the X's.

The fact that the lasso can make the coefficient estimates exactly zero when lambda is sufficiently large relies mostly on a mathematical argument which is not very important for Exam PA. It has to do with the geometry of the contours of the penalty function. If you are interested, please read pages 221-222 of Introduction to Statistical Learning.
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  #107  
Old 10-27-2019, 10:43 AM
ThereIsNoSpoon ThereIsNoSpoon is offline
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I'm already a bit decent with R so some of this stuff isn't a problem. Completed all the modules + exercises too. I'm also looking at the exam SRM sample questions...?

I'm just not sure how to prepare for this kind of five-hour thing. I've downloaded all the practice projects and past exams, so would giving them in exam-esque conditions on weekends, say every Saturday, help out? What else is there?
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  #108  
Old 10-28-2019, 01:14 AM
ynyay ynyay is offline
 
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Originally Posted by TinyTim7 View Post
I think it is a first-time user discount. When I go on the website without being logged in, most of the courses are showing as around $200 with a slash through it, and the price reduced to $11.39


Is it available now? I gonna take education, but it seems to be unvalid


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  #109  
Old 10-28-2019, 11:50 AM
jonniemarko jonniemarko is offline
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Is it available now? I gonna take education, but it seems to be unvalid
I got it this weekend, but when I signed up to purchase, the price jumped up to $18.49 with no explanation... Weird, but it's better than $200.

Hoping that this + ISLR + modules + old exams will be enough... has anyone heard about the manual's release? I'm working through everything else, but would feel a lot better if that was out.
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  #110  
Old 10-28-2019, 03:01 PM
Yossarian Yossarian is offline
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I've posted this elsewhere, and at the risk of making it the mean grade go higher, making it harder to pass ... read this CAS monograph on GLMs

https://www.casact.org/pubs/monograp...hare-Tevet.pdf

It is super helpful and written for practical use. It should be included in the exam materials IMO, that is how relevant it is (mostly Chapters 2, 3, 4, 5, 6.1, 7.3). I should have read it before taking and failing the last exam!
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