Thread: Mean and Standard Deviation....

Alright, I am working a problem, can't quite figure out how we arrive at the answer in the book-

Here it goes:

Specifications for a part for a dvd player state that the part should weight between 24 and 25 ounces. The process that produces the parts yields a mean of 24.5 ounces and a standard deviation of .2 ounces. The distribution of output is normal.

a) What percentage of parts will not meet the weight specs?
b) Within what values will 95.44% of sample means of this process fall, if samples of n=16 are taken and the process is in control (random)?

I figured on a) that we would use the z= x-m(mu)/standard deviation....but I'm not sure where I am going with this.

Can anyone help me with this? I'm not understanding how to arrive at any real "answer".

Thanks!!

The probability that a sample will not specifications, would mean it has a value of what - "24 to 25", or "less than 24 or greater than 25"? You have to learn (fairly quickly) how to translate some of this stuff into real world language. Relying on formulas isn't going to help you much with stats, if you do not know how or when to use them.

Ok, so how would I go about solving this problem? I'm stuck with no real definitive way to solve in the book and I can't figure out how they came up with an answer. I'm really lost. Thank you for your help!!