4 The catalyst for a fluid-bed reactor is prepared in single batches and used one at a time without blending. Tetrahydrofuran (THF) is used as a catalyst precursor solvent. During the impregnation (SIMP) step the liquid precursor is precipitated into the pores of the solid silica support. The solid catalyst is then reduced in the reduction (RED)

step using aluminium alkyls. The THF level is an important process parameter and is measured during the SIMP and RED stages.

The following data were collected on batches produced during implementation of a new catalyst family. These data include the THF level on each batch at the SIMP step and the THF level on the final reduced catalyst.

The specifications are: USL LSL THF–SIMP 15.0 12.2 THF–RED 11.6 9.5 Other types of control charts for variables 187 196 14.2 11.1 205 14.5 11.4 207 14.6 11.7 208 13.7 11.6 209 14.7 11.5 210 14.6 11.1 231 13.6 11.6 232 14.7 11.6 234 14.2 12.2 235 14.4 12.0 303 15.0 11.9 304 13.8 11.7 317 13.5 11.5 319 14.1 11.5 323 14.6 10.7 340 13.7 11.5 343 14.8 11.8 347 14.0 11.5 348 13.4 11.4 349 13.2 11.0 350 14.1 11.2 359 14.5 12.1 361 14.1 11.6 366 14.2 12.0 367 13.9 11.6 368 14.5 11.5 369 13.8 11.1 370 13.9 11.5 371 13.7 11.0 372 14.4 11.5 373 14.3 11.9 374 13.7 11.2 375 14.0 11.6 376 14.2 11.5 377 14.5 12.2 378 14.4 11.6 379 14.5 11.8 380 14.4 11.5 381 14.1 11.5 382 14.1 11.4 383 14.1 11.3 384 13.9 10.8 385 13.9 11.6 386 14.3 11.5 387 14.3 12.0 389 14.1 11.3 390 14.1 11.8 391 14.8 12.4 392 14.7 12.2 394 13.9 11.4 395 14.2 11.6 396 14.0 11.6 397 14.0 11.1 398 14.0 11.4 399 14.7 11.4 400 14.5 11.7 Carry out an analysis of this data for the THF levels at the SIMP step and the final RED catalyst, assuming that the data were being pro- vided infrequently, as the batches were prepared. Assume that readings from previous similar campaigns had given the following data: THE SIMP 14.00 0.30 THF-RED 11.50 0.30.