I\'m having trouble understanding when to use the standard deviation or the samp
ID: 3265491 • Letter: I
Question
I'm having trouble understanding when to use the standard deviation or the sample standard deviation. The class provided solution to the problem below did not use the sample standard devation which I know as (standard deviation/sqrt(n)). What is the rule of thumb when to use the sample standard deviation? Why does this problem not use it when they say the standard deviation was derived from taking many samples of size n=4?
PLEASE READ MY QUESTION AT THE TOP. I DO NOT WANT A SOLUTION TO THE QUESTION AS I ALREAD HAVE IT (twice now thanks to previous person answering prior post without reading my question at the top)!!!!!!!!!!!!!!!!!!!!!!!!!!
3.14 .After taking many samples of size n 4 of the 3.14 After taking manv samples of size n 4 of the length of a pipe, Ax and Ox were determined to be 0.973 and 0.003 meter, respectively. The process is in good statistical control and the individual lengths seem to follow the normal distribution. (a) What percent of the pipe lengths would fall outside specification lim- (b) What is the effect on the percent conforming to specifications of cen- (c) What would the effect be if,4x = 0.973 meter and the process stan- Represent each situation above by providing a graphical representation. its of 0.965 ± 0.007 meter? tering the process? dard deviation were reduced to(-0.0025 meter?Explanation / Answer
Okay, sample standard deviation which YOU know as (standard deviation/sqrt(n)) is used when we do some tests or , try to calculate probability for sample mean.
that means, suppose
1. the SD is givem to be something
2and a sample of size n has been drawn
3. and we have been asked to compute probability than sample mean lies between a and b.
then we would devideit by n.
here the calculation is not for sample mean. so we dont devide.
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