One question is why do Chi-sqare rather than a t-test?

You have two samples, and a proportion from each who did something.

And you can then get a confidence interval around the difference.

However, on the data you gave, it seems to me like your conclusion is correct. It just might be a type 3 error - solving the wrong problem

The other big question is, whether or not any test is significant or not, you care, on a substantive level, about the difference in the two rates. Even if 6.9% and 6.4% are exactly the right values, would you want to go ahead?

HTH

Peter L. Flom, PhD Assistant Director, Statistics and Data Analysis Core Center for Drug Use and HIV Research National Development and Research Institutes 71 W. 23rd St New York, NY 10010 (212) 845-4485 (voice) (917) 438-0894 (fax)