The tensile strength of a certain steel is 17.8. The value was determined by finding the average of samples of size 6. The average range
was 2.4.
(a) Calculate control limits for averages and ranges.
(b) Additional sample ranges of 1.4,1.3,1.5, and 1.2 were measured.
Is the range in control?
(c) The means of the samples in part (b) were 18.0, 19.2, 18.5, and
16.0. Are the averages in control?