Question : The table gives $10$ samples of three measurements, made during a production run. Use the statistical process control method to find the indicated control limits.
Using $k_2=2.568$ and $k_3=0$, find the upper and lower control limits for the sample standard deviations.
Options
$a. \;0,\;3.57\\b. \;0,\;3.93\\c. \;0,\;3.70\\d. \;0,\;4.21\\$
My Attempt : I understand that I have to find the means of each sample number, but I'm unable to get the correct standard deviations. or understand the process going for ward using the numbers $k_2 = 2.568$ and $k_3 = 0$. A basic rundown of the process would be much appreciated.