He contends that the data that Tony wrote is uncertain because there is less data available on Washington than California, so he propses using a confidence interval of at least 97.5%, which puts California in the lead. Lowering the confidence interval even more would give California an even greater lead.
That's just silly. A confidence interval by definition is a range; the commenter is arbitrarily choosing to post only the low end of that range. If the high end were posted instead, Washington's lead would look that much more impressive.
That's not to say the math is useless; a better statement (which could have been supported by the data) would have been "The difference between CA and WA is less than the measurement margin of error given WA's small sample size".
You should read the comment in the original post (http://www.tonywright.com/2009/should-you-move-your-startup-...) by user abscondment.
He contends that the data that Tony wrote is uncertain because there is less data available on Washington than California, so he propses using a confidence interval of at least 97.5%, which puts California in the lead. Lowering the confidence interval even more would give California an even greater lead.