[gumpzilla]

[ QUOTE ]

2. student makes 10 1second measurements of the disintegration of a sample of a long lived radioactive isotope and obtains the following values:
3,0,2,1,2,4,1,2,5

how long should person count to establish an uncertainty of 1 percent?

i hardly know what theyre asking for here. half life?

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So in 10 seconds, you have 20 counts. So assume the average rate is 2 counts per second. The physics aspect is that you're supposed to know that the uncertainty for this kind of random process goes like root N, where N is the number of counts. Put into relative terms, like the question asks for, the relative uncertainty should go like 1 over root N. That will be one percent when root N is 100, or N = 10000 counts. At 2 counts per second, that should take about 5000 seconds.