[0xff00ffee]

Really? Huh. I thought confidence interval mattered which is proportional to sample size, e.g. bigger is always better.

So more samples is worse for a study like this?

Seems counter-intuitive, but I'm not a stats guy.

[snapetom]

For things like polling, yes. Bigger is better. But scientific studies deal with the question "does this have an effect." In that aspect, you introduce Type I and Type II errors, and sample sizes play into the chances of making them.