statistics help

Daniel E. Cox decox at
Mon Nov 3 22:25:16 EST 1997

To all biostatistician and/or immunologists,

We are developing a bacterial vaccine and are studying the use of an
in vivo immunogenicity assay for potency and stability testing.  Our
approach has been to simply immunize a group of mice (10-15) and
determine the final titer of each animal against a purified antigen
from the bacteria by EIA.  We generally see a very wide range in
titers, often up to 5 logs.  We are presently optimizing our system
and are in discussion regarding the best way to analyze these data.
We are attempting to use this technique to compare one vaccine
preparation against another to determine if a particular preparation
is more or less active than a reference preparation, and need to know
the best approach to determining significant differences.   I have
several specific questions regarding the most appropriate way to

- Is it more appropriate to perform the statistical calculations on
unmodified titer data or to use a log of the individual titers?

- Similarly, is it more appropriate to compare groups by arithmetic
means of titers or geometric means? and  why?

- When comparing groups of animals, what is the most appropriate
statistical method for assessing significance?  I have used Student's
t-test, dominance statistic and Wilcoxon-Mann-Whitney test.  It is not
clear to me which, if any, of these techniques will yield the
appropriate answer.  Is there another that may be more useful (and

- Can anyone suggest either references or books in which statistical
analysis of immune responses is discussed?  I would prefer information
sources aimed at the non-statistician.

If there is anyone out there with experience in developing
immunogenicity assays such as these and would be willing to share
their insights, it would be most appreciated.

Thank you in advance

Daniel Cox,  Ph.D.
Worcester, MA USA

decox at

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