Jarmo Now there's a good question. At any given point on the time scale, provided you express the value in arithmetic ohms and not in log10 ohms, I would say the arithmetic mean and variance or SD. However, I believe that this is relatively meaningless unless you wish to plot the whole time x R curve with SD limits, because the curve is probably noisy. If you wish a mean end-value, I think you should average all the readings over the last several hours. Better still, use exponential curve-fitting techniques on all the plots over the total time and average plus SD each of the parameters and plot a new curve from this: this would be the best statistical method, requiring a little number-crunching using a good mathematical software (don't try it in a spreadsheet application: you'll come to a very sticky end, it's a promise!). Brian Kiiski Jarmo wrote: > To estimate the average of SIR-test results should arithmetic or geometric > mean used and how standard deviation should calculated? > > B.R. > Jarmo Kiiski > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with following text in > the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional > information. > If you need assistance - contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################