Statistics and probalbility

(b) A TiW layer is deposited on a substrate using a sputtering tool. The table below contains layer thickness measurements (in angstroms) on 20 subgroups of four substrates. Setup X and R control charts on this process. Comment whether the process is in control or not. Revise the control limits as necessary and assume all the assignable cause was identified. All your answers should be rounded to 4 decimal places. (14 marks) [Total : 25 marks] Subgroup X1 X2 X3 XA Subgroup X1 X2 X3 X4 459 449 435 450 11 445 452 453 438 443 440 442 442 12 456 457 436 457 457 444 449 444 13 459 445 441 447 469 463 453 438 14 441 465 438 450 DO YOUI A W N H 443 457 445 454 15 460 453 457 438 444 456 456 457 16 453 444 451 435 445 449 450 445 17 451 460 450 457 446 455 449 452 18 422 431 437 429 444 452 457 440 19 444 446 448 467 10 432 463 463 443 20 450 450 454 454