First, notice that the correlation coefficient between total payroll and winning percentage is 22.4%, which means that the two variables move together just over 22%; or there is about 78% not moving together. That does not seem to me a great deal of support for the hypothesis that as team's spend more on payroll, it results in higher team winning percent (or better quality teams).
Second, we I run a regression (including a constant term), I find that payroll for the 2010 season is statistically insignificant. In other words in statistical terms payroll has zero effect on winning percentage at this point in the season. From that I would conclude that payroll for the 2010 MLB season has zero impact on winning percent in the 2010 season. Maybe given more time, this relationship will increase and become statistically significant. Over time (in other words adding more seasons) we do find a statistically significant relationship, but it is rather weak, indicating that using payroll to find out who the better teams in baseball will be is not all that reliable.
|Los Angeles Angels||0.491||$104,963,866|
|Los Angeles Dodgers||0.585||$95,358,016|
|New York Mets||0.500||$134,422,942|
|New York Yankees||0.623||$206,333,389|