Posted by Beverley on .
Hi Bob,
Thanks for the direction. I got so far with it on my own and became stuck. I did as you said but still have one question. Would the answer to the question be 1.31 ounces or 6.61 ounces? I feel the answer is 1.31. Thanks
* Statistics  bobpursley, Wednesday, October 6, 2010 at 4:56pm
No. When the mean is zero, the point comes out to be 1.31 ounces. But you want that 1.31 to be 5.3, so you add 5.3 to 1.31, mean 6.61. That way, you at 5 percent is still 1.31 ounces below the mean.
Remember here, you std deviation is .8 ounces, so three standard deviatons is only about 2.4
Ok so the average weight of the product should be around 2.4? Sorry I am just hitting a wall here. I see everything above and it makes sense but I just am struggling to know what the final answer is

Statistics 
bobpursley,
No, the average is 6.61 (the mean). You want no more than 5 percent to be greater than 5.3ounces. With a .8 standard deviation, 5.3 is (1.31/.8=1.6 standard deviations from the mean.)
Go back to http://davidmlane.com/hyperstat/z_table.html the first applet, mean 0, standard deviation .8, below 1.31 and note that the shaded area is .05 That is what you wanted.
your mean: 6.61, std deviation .8
Think all this out, it is very important you understand the distribution curve.
Take a for instance: if you wanted no more than five percent to be 23, what would be the mean? Answer: 1.31 from mean is 23, so mean is 24.31