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mantubiradar19
Quartz | Level 8

Hi All ~ I'm dealing with a contienous variable whose distrubution looks as shown in the two figures. Which tranformation procedure would you recommnend for this kind of distrubution? 


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25 REPLIES 25
mantubiradar19
Quartz | Level 8

I'm using this as the dependent variable for my GLM analysis ~ which assumes the normal distrubution of outcome! 

Reeza
Super User

@mantubiradar19 wrote:

I'm using this as the dependent variable for my GLM analysis ~ which assumes the normal distrubution of outcome! 


Logistic regression falls under GLM and a binary response is definitely not normal. 

 

Ksharp
Super User
Your data is right bias. Try Log Normal distribution.

Reeza
Super User

Box cox transformation using proc transreg may be an option

mantubiradar19
Quartz | Level 8
Can you please educate me more about this transformation with an example? Thanks
mantubiradar19
Quartz | Level 8

The distrubution shown here is the log tranformed values of orifinal values! 

Rick_SAS
SAS Super FREQ

How did you create that panel of histogram + box plot + Q-Q plot?  Is that something you wrote with GTL or was it generated by a SAS procedure?

mantubiradar19
Quartz | Level 8
This is the output from PROC UNIVARIATE!
SteveDenham
Jade | Level 19

That is an interesting plot.  Even the log10 values show an extreme skew.  Is there a possibility that these are maximum values for something?  If so, you may want to look at a Weibull distribution or some other generalized extreme value distribution.  a ln(ln (x)) transformation might be useful.  I don't know if TRANSREG will hande this, though.

 

Steve Denham

mantubiradar19
Quartz | Level 8
I tried the ln(ln(x)) ~ The distribution almost looks the same with the reduced SD!
mantubiradar19
Quartz | Level 8

Here are the log(x) and log(log(x)) distrubution! 


Capture.JPG
Reeza
Super User

It's hard to see what your doing now, since the forum doesn't sort the responses. So no way to tell which reply goes with which post. In the future please just do one response. This isn't your fault - limitation of the forum. 

 

Did you post your original distribution? Also, what is the variable, in laymans terms. Context can help with deciding what type of transformation to use, and there are certain standard transformation in diff industries. 

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