31 May 2010

Seasonal adjustments for weekly series

I've been trying to learn the software from the Fed that does seasonal adjustment for weekly series. The software is not user-friendly, so it's been a difficult learning curve. Tom Evans at BLS is working on a SAS interface that will make the program easier to use, but the interface is still in development. Tom has been helping me learn the program, and he helps me fix my errors when I make a mistake because error messages are nonexistent in the program. I was also having trouble getting the program to run on my series, and I believe it's because my series are short, so the program has trouble estimating holiday effects.

In the short term, I have found that I can get something like looks like a seasonal adjustment from X-12 if I ask for a trend. I can get it almost as smooth or as rough as I would like by changing the trend filter length. With a limit on the Henderson filters of 101, and with a period of 52 (and sometimes 53), the very longest trend doesn't really look like a trend because you can still see the seasonality. But with a very short trend, it is very close to what I get from the Fed's program. So in the short term, I like what I get from X-12, and it's a lot easier to use.

19 May 2010

AP Statistics rain date

The AP Statistics rain date was today. My oldest went into the test site a bit apprehensive, but she found a seat with decent lighting, and when she left, she was smiling. My first foray into teaching AP Statistics, and so far it seems like a success.

08 May 2010

Flooding in Middle Tennessee

In seasonal adjustment, we are very often looking at series with unusual values, and often I'm looking for natural disasters that have caused problems in my series. This week, the natural disaster has been in my backyard.

If you live outside of Nashville, you may not have heard, but Middle Tennessee was hit by a huge flood last week. The national news coverage gave us 15 minutes, mostly due to a failed car bomb in Times Square. Though I understand that terrorism is a real problem, what is happening in Tennessee (and the Gulf of Mexico, I might add) seems to me to be more important.

Nashville had its highest rainfall totals since records began. The Cumberland River and every other river in the area crested at their highest levels in over 80 years. People drowned, some of them stuck in their cars in Interstate-24. The cost of the damage is in the billions; it might be the costliest non-hurricane disaster in American history. It is the single largest disaster to hit Middle Tennessee since the War Between the States.

At our house, the flood waters reached almost to the barn, the highest we've ever seen the creek overflow its banks. Fortunately, we were all here on Saturday, and our house sits high on a hill and is quite waterproof, even when there is more than 15 inches of rain in a single day. My husband had to wade across the creek in the lightening to get to work early this week, but he made it through and back home again. My oldest daughter's AP test was postponed until May 19 (and she was really ready to have it finished), and my middlest daughter couldn't get her braces off because her orthodontist lost his car in the flood and couldn't get to the office.

Maybe the best part of the story is that Nashville isn't on the news. Maybe it's because there was no major looting, no major breakdown in rescue operations. The stories on the local news are about high school kids that are helping people clear the belongings from damaged houses and neighbors who were pulling their neighbors off rooftops using canoes or jet skis. We saw this same kind of cooperation after the big tornado in Murfreesboro just over a year ago. Maybe Nashville and the rest of Middle Tennessee isn't on the national news because in spite of the disaster, there isn't so much bad news in Middle Tennessee.

I'm so proud to be living in Tennessee. I'm so proud of how we all come together and take care of each other.