# cbloom rants

## 12/03/2006

### 12-03-06 - 1

Evaluating the "Need A Win" hypothesis.

A lot of people in Sports Betting use the motivation of the two teams as a basis for choosing the side to bet. The theory is that the team that needs a win is more likely to play to full effort and beat the spread. I've always been skeptical of these theories and thought I'd try to statistically examine how important this theory actually is.

I examined all the NFL games from 1999 to 2006. For each game I made a rough evaluation of which of the teams "needed a win". Only games in weeks 8-14 were examined, which is the heart of the playoff run. Teams that "need a win" were any teams with a record >= 50% wins and with a record worse than 8-2. Generally these are the teams on the bubble for their division or a wild-card spot. Note that this isn't a totally precise measure of "need a win" but it should be good enough to see some statistical correlation if any exists.

Here are the results. There are four categories :

```cat 0 = both teams don't need a win
cat 1 = road team needs a win
cat 2 = home team needs a win
cat 3 = both teams need a win

The results are (home wins)-(home losses)-(pushes)
ATS = Against The Spread

32 teams, 1992 games

cat 0 WLP : 827-578-0
cat 0 ATS : 678-683-44
cat 1 WLP : 84-125-0
cat 1 ATS : 103-100-6
cat 2 WLP : 138-65-0
cat 2 ATS : 94-102-7
cat 3 WLP : 105-69-1
cat 3 ATS : 91-76-8
```

In particular look at categories 1 and 2. The team that needs a win is 263-149 vs. teams that don't need a win. However, they are only 194-205 ATS !!

Now, is that W-L record even significant? The fact is most of the time you have a "need a win" vs. "dont need a win" matchup it's a pretty good team vs. a very bad team, so it's no surprise that they win a lot more.

For comparison I did the same study, but just grouped based on teams with a record >= 50% against teams with a record < 50% , eg. winning teams vs. losing teams.

```32 teams, 1992 games
cat 0 WLP : 219-136-0
cat 0 ATS : 177-169-9
cat 1 WLP : 186-268-0
cat 1 ATS : 224-213-17
cat 2 WLP : 328-111-0
cat 2 ATS : 216-211-12
cat 3 WLP : 421-322-1
cat 3 ATS : 349-368-27
```

Winnings teams are 596-297 against losing teams, which is actually a better ratio than the "need a win" vs "dont need a win".

It's possible that a better measure of "need a win" would reveal a slight statistical significance, but the absense of any here indicates it is not strong at all.