Suppose There Are 10 Sample Obtained at Equally Spaced Time $a _ { 4 }$

Multiple Choice

Suppose there are 10 sample obtained at equally spaced time points, and n=4 observations in each sample. If the sum of the 20 sample standard deviations is 42, and that the tabulated value of $a _ { 4 }$ is .921, then the 3-sigma control limits LCL and UCL for an S control chart are respectively

A) 1.062 and 3.138
B) 3.138 and 4.765
C) 0.0 and 4.765
D) -.354 and 4.554
E) -.565 and 4.765