Another Little Gem

Here's another great little free program, G*Power 3. It does many of the common anova power analyses but also includes manova and Hotelling's T-squared. Throw in multiple regression and you have a pretty useful package.

There are versions for both windows and macs. This in itself is pretty unusual.

The authors are Franz Faul, Edgar Erdfelder and Axel Buchner. They all appear to be psychologists but that is no reason to avoid G*Power. I highly recommend it. The website is at Heinrich Heine University Dusseldorf and here is the link.

pbe

What The Heck(man) Is Going On?

We had a client come in with a question about a Heckman selection model that was giving her trouble. She had run it several weeks earlier and everything was working fine. She had some missing data among her predictors and decided to do a multiple imputation. After imputing the missing data she got the following error message:

     Dependent variable never censored due to selection.

She couldn't figure out what was wrong until I asked her if she had also imputed the response (dependent) variable. Instantly, she realized what the problem was. Since she had imputed all the variables in her dataset, there were no longer any missing values on her response variable and therefore no way to estimate a selection model.

pbe

Parallel Universe

I am a Mac user. This creates problems in that there are several stat packages that only run on Windows. For the past couple of years the solution has been for me to Timbuktu into a campus computer to use Windows based software. This solution is relatively slow and clunky.

That was then, this is now. I have installed Parallels Desktop on my relatively new MacBook Pro. Then, after a few hours installing Windows and a few more hours installing stat software (I had problems installing SAS), I'm all set to go. I now run Mplus and SAS on my Mac. And actually, they run pretty fast as long as I close down some of the larger programs on the Mac side. Overall, my throughput is much faster than when I was using Timbuktu. So, for now, I am a happy camper working in a parallel universe.

pbe