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R: st: one-way 95 CI for Ha: diff < 0

From   "Carlo Lazzaro" <>
To   <>
Subject   R: st: one-way 95 CI for Ha: diff < 0
Date   Mon, 16 Jun 2008 19:13:15 +0200

Dear Tony,
thanks a lot for your kind and useful insight about my previous thread.
In fact, I was interested in a lower bound for Ha: diff < 0 in qalys to be
aware of the LL concerning departure from -0 for this variable.
I used this and other results to figure out how the joint density function
of incremental cost and qaly might lay on the cost-effectiveness plane (for
all the Statalisters coming from other research fields, I take the liberty
to provide the following reference: Briggs A, Schulpher M, Claxton K.
Decision Modelling for Health Economic Evaluation. Ohford: Oxford University
Press, 2006) for two fictitious health care programmes
Thanks a lot for your kindness and for your time.
Kind Regards,

-----Messaggio originale-----
[] Per conto di Lachenbruch,
Inviato: luned́ 16 giugno 2008 17.45
Oggetto: RE: st: one-way 95 CI for Ha: diff < 0 

It's not clear whether you want to get an upper bound or a lower bound
for the difference.  In the intervals given by Maarten and Svend give an
interval that says the difference is at least the lower bound.  But you
may want an interval that says it's no more than the upper bound.  In
particular, if the upper bound is less than 0, then the inference is
that the difference is significantly less than 0.


Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001

-----Original Message-----
[] On Behalf Of Maarten buis
Sent: Saturday, June 14, 2008 2:00 PM
Subject: Re: st: one-way 95 CI for Ha: diff < 0 

--- Carlo Lazzaro <> wrote:
> after performing the following ttest, I would like to know about a
> possible way to obtain with Stata 9.2/SE the one-way 95 CI for Ha:
> diff < 0.

ttest qaly, by(treat) unequal level(90)

choose the left confidence limit.

-- Maarten

Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

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