The Parent Trap

Here is a question emailed to us by a client:

I have 4 variables from which I want to create a new variable.

v1 = do you live with mom? (0, 1)
v2 = do you live with dad?
v3 = do you live with stepmother?
v4 = do you live with stepfather?

I want to create a variable PCOMP and code
1 if live with mom and dad
2 if live with mom and stepfather
3 if live with stepmother and dad
4 if live with mom only
5 if live with dad only
6 Other

I'd also like to identify who is from a two-parent household.

How do I do this?

There are many ways this could be handled, here is the one I suggested:

pcomp = v1 + 10*v2 + 100*v3 + 1000*v4

recode pcomp 11=1 1001=2 110=3 1=4 10=5 else=6

two_parent = pcomp < 4

Note: This is in pseudo-code and can be adapted to any stat package that supports recode. Also, the client will have to decide how to deal with missing values as this approach will not work with missing values for v1-v4.

pbe

Power Series

Today we had the second in our series of three power analysis presentations. Jason Cole (UCLA alum and outside consultant) talked in depth about effect size, the proper alpha level and multiplicity issues to an audience of 42. Within the next week, we hope to post the audio portion of Jason's presentation along with a pdf of his powerpoint slides.

Last week, for Christine's presentation, we had almost sixty people in attendance. This created problems because the Visualization Portal is not meant to hold that many people. For this week's presentation we had to have people register on-line to limit the number attending.

We are looking forward to another big crowd for our third power analysis presentation in two weeks.

pbe

A Rose By Any Other Name...

UCLA Academic Technology Services Statistical Consulting is pleased to announce that Rose Medeiros starts work today as our new full-time stat consultant. She comes to us from the University of New Hampshire where she is completing her PhD in sociology. She just spent the last five days driving cross country with her mother and her one-eyed cat named Bentley.

Rose has experience using SPSS, Stata, HLM, Mplus and sometimes R. She "enjoys" multilevel modeling, longitudinal data analysis and structural equation modeling.

And, of course, Rose is "famous" for the Stata ado-program -njc- that provides timely quotes from the statistically-minded geographer Nicholas J Cox (note: the -njc- program does not use maximum likelihood estimation).

Please drop by walk-in consulting and say "Hi," to Rose.

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A Little Gem of a Program

A tip by legendary stat consultant Michael Mitchell pointed us to a little gem of a program, Optimal Design.

Optimal Design does power analysis for a wide variety of multilevel level and repeated measures designs. The program is a product of the Survey Research Center of the Institute of Social Research at the University of Michigan. The program is fast, easy to use, and the best part, it's free. You can find out about it at http://sitemaker.umich.edu/group-based/optimal_design_software.

This program comes at an opportune time for us since ATS Stat Consulting will be giving the first of three presentations on power analysis starting next Wednesday, February 14, 2007 at 10am. The other two presentations will be Feb 14th and Mar 7th.

pbe