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  #251  
Old 05-29-2019, 10:30 AM
Gettin Lucky In Kentucky Gettin Lucky In Kentucky is offline
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Is anyone planning on taking an FSA exam in the Fall? Will you begin studying right after this exam is taken? I have everything on my transcript for ASA except PA and APC (July) and don't really want to waste time.
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  #252  
Old 05-29-2019, 12:05 PM
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TranceBrah TranceBrah is online now
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Quote:
Originally Posted by Gettin Lucky In Kentucky View Post
Is anyone planning on taking an FSA exam in the Fall? Will you begin studying right after this exam is taken? I have everything on my transcript for ASA except PA and APC (July) and don't really want to waste time.
I'll be doing LPM in Oct. The good thing about PA timing is that you don't need to know your result before deciding to start studying for next exam. If you fail, then you have all of November to study for PA again.
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  #253  
Old 05-29-2019, 01:13 PM
Josh Peck Josh Peck is offline
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Originally Posted by noone View Post
Thanks. So the examples in module 7 use issage (predictor) for the x-axis and yhat on the y-axis. What does y-hat mean? The target variable is claim count and is either C (actual_cnt=0) or N(actual_cnt>=1).
The y axis is the log odds.
This is because, for GLMs the linear part equals g(mean).
Where g() is the link function.

Note that When the log odds = 0, the probability = 0.5
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  #254  
Old 05-29-2019, 01:15 PM
Josh Peck Josh Peck is offline
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It makes no difference to use sensitivity vs specificity as long as you know how to interpret it, which it seems that you do. It simply depends on which factor level is labeled as TRUE.
Does anyone know how to easily switch the levels though?
While it doesn't really matter, it is an inconvenience.
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  #255  
Old 05-29-2019, 03:45 PM
Adapt and Chill Adapt and Chill is online now
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Originally Posted by Josh Peck View Post
Does anyone know how to easily switch the levels though?
While it doesn't really matter, it is an inconvenience.
Yeah, you can pass an argument for the positive class. Per ?confusionMatrix:

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positive - an optional character string for the factor level that corresponds to a "positive" result (if that makes sense for your data). If there are only two factor levels, the first level will be used as the "positive" result.
## Default S3 method:
confusionMatrix(data, reference, positive = NULL,
dnn = c("Prediction", "Reference"), prevalence = NULL,
mode = "sens_spec", ...)
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  #256  
Old 05-29-2019, 04:06 PM
Josh Peck Josh Peck is offline
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Yeah, you can pass an argument for the positive class. Per ?confusionMatrix
Nice! I never took note of the argument before
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  #257  
Old 05-29-2019, 04:11 PM
Josh Peck Josh Peck is offline
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Does anyone have info on how to pick a good cutoff value for classification predictions?

I would assume you use the ROC curve and pick a cutoff such that your cutoff is close to 0 without seeing a dropoff in the ROC Curve.
However I have no idea how to actually use this idea in practice.

Edit:
I actually found an answer to this fairly quickly.
Check out the link below
https://stats.stackexchange.com/ques...imple-function
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Last edited by Josh Peck; 05-29-2019 at 04:58 PM..
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  #258  
Old 05-29-2019, 05:31 PM
Yossarian Yossarian is offline
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Originally Posted by Adapt and Chill View Post
Yeah, you can pass an argument for the positive class. Per ?confusionMatrix:



## Default S3 method:
confusionMatrix(data, reference, positive = NULL,
dnn = c("Prediction", "Reference"), prevalence = NULL,
mode = "sens_spec", ...)
another way, using the "Student Success" solution code for the variable Train.DS$G3.Pass.Flag:

> contrasts(Train.DS$G3.Pass.Flag)
.. P
F 0
P 1

the contrast table shows you that Fail = 0, Pass = 1, with binarization of F left out

you can relevel this with :

> contrasts(relevel(Train.DS$G3.Pass.Flag,"P"))
.. F
P 0
F 1

now Fail = 1, Pass = 0, with binarization of P left out

I THINK. I believe contrasts shows you how R "dummifies" the levels ...

Last edited by Yossarian; 05-29-2019 at 05:52 PM.. Reason: Added .. to the P and F, as they weren't aligning above their respective columns
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  #259  
Old 05-29-2019, 10:34 PM
Gettin Lucky In Kentucky Gettin Lucky In Kentucky is offline
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Quote:
Originally Posted by TranceBrah View Post
I'll be doing LPM in Oct. The good thing about PA timing is that you don't need to know your result before deciding to start studying for next exam. If you fail, then you have all of November to study for PA again.
Those were my thoughts as well. Thanks for the confirmation. 2019, Thanks for handing me another year without having a life.
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  #260  
Old 05-30-2019, 06:51 PM
noone noone is offline
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Does anyone know if we are able to use the ? function that exists withing R during the exam?
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