1. The problem statement, all variables and given/known data We want to measure the specific activity (number of decays per second) of a radioactive source so that we can use it to calibrate the equipment of the gamma-ray experiment. We use an electronic counter and a timer to measure the number of decays in a given time interval. In round numbers we measure 1000 decays in 5 minutes of observation. For how long should we measure in order to obtain a specific activity with a precision of 1%? Explain. 2. Relevant equations 3. The attempt at a solution I'm not sure where to begin. I thought about using the formula 1/sqrt(N), but wasn't sure if I could set that equal to the percent of precision (1%). I also hope I put this question in the right category. Thanks in advance!!