variance division

1. standard deviation of a division

Hi, I have a rather easy question: I have a batch of different dried fruits, let's say n=100, with a diameter of 8±2 cm, 2 being the standard deviation. After throwing them in water the distribution of the batch's diameters is let's say 16±5 cm because of the swelling. This results in a size...
2. division of variance

Hi, My situation is that I have mean and standard deviation for the detection rate of widgets based on repeating *many* times observations when there was a known number of widgets present. Then I have a second scenario where I have an unknown number of widgets, and I observe *several* times and...