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From |
"Cathy L. Antonakos" <cathya@umich.edu> |

To |
Statalist <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: equivalence tests |

Date |
Tue, 10 Jul 2007 18:54:20 -0400 (EDT) |

On Wed, 11 Jul 2007, Joseph Coveney wrote:

Also, I'm curious as to what problems Celine had in resolving the results in the Stata Technical Bulletin article for -equim- and -equip with formulas in the Hwang and Morikawa review article (full text at http://www.diahome.org/content/abstract/1999/d3341205.pdf ). Joseph Coveney

Joseph, I had the problem with resolving results in two different sources, not Celine. The difficulty was in taking output from the STB article for -equim- and plugging those numbers (mean, sd, n) into the Hwang & Morikawa formulas for Z1 = (d + delta) / s_d lower limit of the one-sided CI = ( 2 - Z_0.95 * s_d) Z3 = d / s_d where d = the difference between means, s_d = sqrt(2 * s^2 / n1), and s is the pooled SD. I was not clear on what to pay attention to in the unfamiliar -equim- output. It would have been convenient to figure out a way to use parts of the output as input for determining non-inferiority and superiority of a non-standard method. Z1 and the lower limit of CI are used in Hwang & Morikawa, to establish non-inferiority for a given delta. Z3 and the lower limit of CI are used to establish superiority. To try to get clarity on any pieces of the -equim- output I could use, I tried matching up the STB results with results I calculated by hand using the Hwang & Morikawa formulas. I couldn't get them to match. Another problem was that d (difference between means) in Hwang & Morikawa was not identified as the absolute value of the difference, but I think it should have been. I could be wrong about that. This method is not what I would have chosen. My hunch is that introducing delta, which is not generated from the data, into equations with parameters that are generated by the data, creates problems. I could be wrong about that, too. That's all I have. HTH. Cathy Antonakos * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: equivalence tests***From:*Joseph Coveney <jcoveney@bigplanet.com>

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