Looking at Time Series, Part 2

In part one, I looked at time series analyses of my 2008-09 college gambling results and it wasn't pretty.

Tonight, I'm going to look at 2007-08, since most of my contrarian thoughts were forged during that period and, conveniently, I have statistics for them.

The graph from the 07-08 NCAAB season is shown below. It has an uptrend (that'd be nice), so I'm probably going to have to look at the first differences.

Now here is an interesting result. At first glance, it almost looks like a random walk again.

Type Coef SE Coef T P
AR 1 0.9881 0.0156 63.18 0.000
Constant 0.2549 0.1641 1.55 0.122
Mean 21.34 13.74

But, remember, I said I have to look at the first differences because of the upward trend. Here is the time series analysis on the first differences.

Type Coef SE Coef T P
AR 1 0.1142 0.0631 1.81 0.071
Constant 0.1444 0.1532 0.94 0.347

The constant term is not statistically significant, which kind of sucks. If it were significant, it would indicate skill. Regardless, the AR1 coefficient is marginally significant. I'm not sure if that really means there was predictive ability in 2007-08, but at least it shows statistically that I was more likely to win the game after a win (and lose after a loss).

The college football season from 2007-08 also had a positive trend (below), so a similar analysis will need to be completed on the first differences.

For the 2007-08 NCAAF data, the trend was so severe, the time series program died before converging, so we'll have to go straight to the first differences.

Type Coef SE Coef T P
AR 1 0.0203 0.0838 0.24 0.809
Constant 0.4808 0.2598 1.85 0.066

This is what I wanted to see all along. The AR1 term for the first differences is very close to zero and the constant term is positive and statistically significant. Basically, that is saying that each bet was totally independent and had an expected outcome of 0.5x. Statistical skill, finally.

For completeness, I suppose I should look at 2008-09 college football from Week 3 forward. Intelligently, I didn't even play the NCAAF in Week 2.

Not much change from the original.

Type Coef SE Coef T P
AR 1 0.0095 0.0856 0.11 0.912
Constant 0.5586 0.2693 2.07 0.040

No real change in time series statistics either. Hooray. One good season in the last six.

Clearly, I think the results show I had some skill in 2007-08. Whether that is attributed to blind luck, a different gambling market, or strategy changes causing a decline in my abilities, I'm not sure. Since it seems that contrarians in general have records that are worse this year overall compared to last, I'm hopeful, but not convinced, that 2008-09 is just a hiccup on the path to success.