Gib- Many statistics packages allow you to create a "probability plot" to visually determine whether your data (or a transform of your data) approximates a normal distribution. Like antibody titers, white blood counts, and thymidine uptake data, rare event data (expressed as a reciprocal frequency or as a percent) often approximate a log-normal distribution. We have published this for tetramer data. I would not be surprised if intracellular cytokine measurements are log-normally distributed as well. The best thing to do is to take a look. Albert Donnenberg We are performing intracellular cytokine measurements for evaluation of experimental vaccines and I am wondering about how to express the frequency data. What is more meaningful, the frequency or the logarithm of the frequency? I'll try to put this question into context. When compiling statistics on antibody titers it is standard to compute the geometric mean titer for a group of vaccinees under the assumption that the logarithms of the titers follow a normal (gaussian) distribution. Also, when we compile statistics on lymphoproliferation stimulation indices we calculate the geometric mean for the group of vaccinees. Here we find that the standard deviation of the measured stimulation index is proportional the mean and therefore the standard deviation of the log-transformed stimulation index is nearly constant . Does anyone have any insights into how best to express intracellular cytokine frequency data, linear or log (or other) based on data or on theoretical considerations? Gib Otten Chiron Corp. 4560 Horton St., M/S 4.3 Emeryville, CA 94608 Telephone: 510-923-2965 Fax: 510-923-2586 mailto:Gillis_Otten@chiron.com
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