Contributor
Posts: 57

# What kind of transformation procedure need to applied for this kind of distribution?

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?

Super User
Posts: 23,721

## Re: What kind of transformation procedure need to applied for this kind of distribution?

Why are you transforming?

Contributor
Posts: 57

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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

Super User
Posts: 23,721

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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.

Super User
Posts: 10,778

## Re: What kind of transformation procedure need to applied for this kind of distribution?

```Your data is right bias. Try Log Normal distribution.

```
Super User
Posts: 23,721

## Re: What kind of transformation procedure need to applied for this kind of distribution?

Box cox transformation using proc transreg may be an option

Contributor
Posts: 57

Contributor
Posts: 57

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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

SAS Super FREQ
Posts: 4,241

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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?

Super User
Posts: 23,721

## Re: What kind of transformation procedure need to applied for this kind of distribution?

@Rick_SAS that looks like the output from proc univariate.

Contributor
Posts: 57

## Re: What kind of transformation procedure need to applied for this kind of distribution?

This is the output from PROC UNIVARIATE!
Posts: 2,655

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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

Contributor
Posts: 57

## Re: What kind of transformation procedure need to applied for this kind of distribution?

I tried the ln(ln(x)) ~ The distribution almost looks the same with the reduced SD!
Contributor
Posts: 57

## Re: What kind of transformation procedure need to applied for this kind of distribution?

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

Super User
Posts: 23,721