Question $3$ Mark: $3+3=6$

The checking$-$in time at a readymade garments organization is to be investigated. The means of $15$ samples

of $10$ observations with the ranges for each of the samples are given in minute in the table below:

i$.$ Construct the mean control chart for this process of checking$-$in with three$-$sigma $(z=3)$ limits$.$

ii$.$ Plot the sample means into the control chart. Is the process in control?