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Experimental Errors

As I examined some of the data, I noticed that there were several plots that contained one or two isolated points at a great distance away from the mean. This occurred when I got data with a high number of photon counts (i.e. low rates). Most of these points were much lower than the mean value. I turned to statistics to analyze whether these counts were feasible or not. Statistics tells us that for a normalized distribution, 99.994% of the data lies within 4 standard deviations ($\sigma$) from the mean. For a non-normalized distribution, the same percentage lies within about 7 standard deviations from the mean. I ended up choosing 7 standard deviations to be the limit for whether I should include the counts or not in my data. Therefore, anything that fell outside of this range I interpreted as dropped counts due to experimental error or error from the equipment.

Figure 1: Here is an example of one of the plots where I saw a dropped count. You can see one data point at about 2.5 seconds after the start of the experiment that is isolated from the rest of the counts.


next up previous
Next: Histograms Up: Results Previous: Results
Joey Cheung 2006-09-27