We have two pots with 25 plants each. After an identical treatment we
wait for a week, and then calculate how many of the plants died. We
repeat this "experiment" 20 times, so we end up with 20 pairs of
"survival percantages".
We are interested in determining the accuracy/reliability of our
method. In other words if in the future we use just one pot of 25
plants, what will be the confidence interval of the result.
At the moment we calculate the pairwise differences,
and use the standard deviation of those 20 differences to
estimate the uncertainty of our method. The standard deviation
I end up is relatively large, and if the survival percentage happens
to be high, I get a funny confidence interval where the upper limit
is > 100%, which is clearly impossible.
I have a feeling this is not the best way to go about this,
but I'm unsure what to do. Perhaps use maximum likelihood
probabilities for P("plant dies"), or somehow transform the
data?
Yours gratefully,
Jukka Sinisalo
=================================================================
Instructions for joining and leaving this list, remarks about the
problem of INAPPROPRIATE MESSAGES, and archives are available at
http://jse.stat.ncsu.edu/
=================================================================
