I am a medical Doctor primarily working in malaria research in Thailand.
We are doing in vitro tests to assess the drug sensitivity of malaria
parasites. For evaluation of the results I use the log-probit model
(which is the standard evaluation method for malaria in vitro test) of
SPSS 10, which gives perfect results. However I would like to make the
evaluation easier accessible also to the local health care personnel
(i.e. in Excel because there is no SPSS available and data are currently
recorded in Excel).
Unfortunately my knowledge of statistics is rather limited to the basics
(i.e. regression, t-test etc.). I tried by transforming the drug
concentration into NLog (LN(x)) and the response into probits
(NORMSINV(x)+5) and doing an ordinary linear regression (y=a+bx) to
calculate effective concentrations (EC50, EC90, EC99). Unfortunately the
results are sometimes hardly comparable to the results I get with SPSS
(generally much lower). I also don't really know how to handle 0 and
100% (and I don't know anything about things like maximum likelihood,
weighting etc.). I downloaded the model description from SPSS. Even
though very elaborate the model description from the SPSS-website was
not too much help to a medicine man.
An Example of the data we have:
Drug Dose Response (% of parasites killed)
0 (control) 0
0.3 1.786
1 3.571
3 19.643
10 78.571
30 92.857
100 100
300 100
I know that this is a somewhat complex question, which could take quite
some time to answer so I understand very well if people do not have the
time. However I would be extremely grateful for help.
Thank you for your help
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