Reducing study sizes - sequential design

Hogne Sandvik at
Mon May 29 11:23:51 EST 1995

In ordinary, classical experimentation, observations are examined when
the experiment itself is finished. In sequential experiments, the
observations are examined in a systematic manner as the experiment
proceeds, in order to terminate the experiment at the earliest
possible time.

Sequential experimentation is attractive from many points of view. In
medicine, ethical and economical arguments weigh heavily in favour. An
average saving in study size of about 1/3, compared to a fixed-size
study, is possible.

Many experiments said to be classical are in fact of the sequential
type, because researchers allow themselves informal analyses of the
results before the experiment is finished.  

Would it not be nicer to include these 'looks' into the formal design?
Egil H. Lehmann, GP and statistician, has developed a computer program
(MEDSEQ) that enables clinicians with only a limited background of
statistics to design sequential experiments. It is freeware. More
information is provided here:

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