How do I calculate the sample size

[#1]

I have tested 3 sample bowls for chemical A content. Their chemical A levels are 79, 85,83 ppm, respectively. The averaged chemical A in these 3 bowls is 82.3ppm. Now the target of chemical A content is less than 100 ppm. The total population of bowls is 10000. I would like to know how many sample bowls do I need to test in order to achieve alpha of 0.5 and powder of 80? My understanding is this is a one sample t test sample size question. So under JMP “ sample size and power” -> “one sample mean” , I set alpha equals 0.05, the difference to detect is 100-82.3=17.7 (my thought is I wanted to know if or not the average 82.3 is the same as the target 100?), my biggest question is how to fill out and figure out the estimated standard deviation?

[#2 · Accepted solution]

You would either get that Std Dev from historic tests on the same materials or you would have to best guess estimate it from your current sample. Normally you would have qualified this material at some point...and that would hopefully have included a Std Dev.