The 90% confidence interval for Dunnett's and Newman-Keuls test are no different than the 95 percent confidence interval.

Fixed bug: Prism is not able to compute the 90 percent confidence interval for the Dunnett or Newman-Keuls test. Starting with Prism 3.03 (win) and 3.0c (Mac), this choice is grayed out. Earlier versions offered to compute 90% confidence intervals, but in fact reported 95% intervals.