Very useful reference.
I wasn't clear whether Frank was suggesting that the enquirer would find the answer there, or Jay and the rest of us would find material in its 46 pages that would help us interpret the question. :-)
Brian G Miller, BSc, PhD, CStat
Director of Research Operations
Direct Line +44 (0) 131 449 8044
e-mail [log in to unmask]
Institute of Occupational Medicine
Research Park North
Riccarton
EDINBURGH EH14 4AP
Scotland, UK
Tel +44 (0) 870 850 5131
Fax +44 (0) 870 850 5132
visit the IOM at www.iom-world.org
----Original Message-----
From: Frank Isackson [mailto:[log in to unmask]]
Sent: 26 January 2006 22:14
Subject: Re: sample size in non-inferiority trial
Some time might be usefully spent in reading "E9 Statistical Principles for Clinical Trials" available from the US FDA website: http://www.fda.gov/cder/guidance/ICH_E9-fnl.PDF
Frank Isackson
-----Original Message-----
>From: Jay Warner <[log in to unmask]>
>Sent: Jan 26, 2006 8:40 AM
>To: [log in to unmask]
>Subject: Re: sample size in non-inferiority trial
>
>For the benefit of us uninformed folks, could someone write a short
>piece giving equivalent words (operational definitions) for
>
>Non-inferiority
>
>equivalence
>
>two-side hypothesis for alpha test (group A is equal to group B/
>Group A is different than Group B)
>
>one-side hypothesis for alpha test (group A is equal or less than
>group B/group A is greater than group B)
>
>one-side and/or two-side beta test (power test) for groups A and B
>comparisons.
>
>If my suspicions are right, then Ioanna's questions can be re-phrased
>into typical/common statistical language, and the issue of alpha
>level (0.05 or 0.025) will become 'obvious.'
>
>Besides, I want to know the terms used by medical people. :)
>
>Jay
>On Jan 26, 2006, at 9:33 AM, ioanna gioni wrote:
>
>> Dear all,
>>
>> I need to calculate the sample size for a non-inferiority trial
>> (normal data).
>> I have an issue with the choice of alpha in the sample size
>> calculation formula. I am not sure if I need to set my type error I
>> (alpha) at half the conventional type I error used in two-sided
>> confidence intervals.
>> Unfortunately, I don?t have access to any sample size calculations
>> book that deals with non-inferiority/equivalence issues.
>> Searching in the Internet I found various examples where some
>> calculate the sample size setting alpha to be 0.05 and some setting
>> alpha to be 0.025.
>> I know that for the analysis I need to either calculate a two-sided
>> 95% confidence interval (equal-tailed) and then use the lower bound
>> for testing the hypothesis or calculate one-sided intervals with a
>> coverage probability of 97.5%. My issue is if in the sample size
>> calculation I set alpha as 0.05 or 0.025.
>>
>> Any help would be appreciated,
>>
>> Ioanna
>>
>> _________________________________________________________________
>> Are you using the latest version of MSN Messenger? Download MSN
>> Messenger 7.5 today! http://messenger.msn.co.uk
>>
>
>Jay Warner
>Principal Scientist
>Warner Consulting, Inc.
>4444 North Green Bay Road
>Racine, WI 53404-1216
>USA
>
>Ph: 262.634.9100
>FAX: 262.681.1133
>email: [log in to unmask]
>web: www.a2q.com
>
>The A2Q Method(tm) --- What do you want to improve today?
|