I'm trying to figure out a starting point for conducting statistical analysis on chemical composition of different bars of metal. I have data from about 150 different bars made over the course of a year. Because these bars are final product, I can only take samples from the top and bottom. Currently, we take three random samples from the top and three random samples from the bottom of each bar. The data is averaged to obtain a representative composition for the whole bar.
- The number of samples we are currently taking was chosen at random. If possible, I would like to reduce the number of samples being taken. Is there a way to determine the amount of risk of the error incurred in reducing the sample size?
Also, due to the nature of this product, it is expected that the chemistry of one bar will not be similar to the chemistry of another bar. Additionally, due to the minimum detection value of the equipment, I have left censored data so my sampling distribution isn't normal.