Texas Roadhouse restaurant wants to ensure consistency (quality) in the size of their 16 ounce ribeye steaks. While the process was in in control, cA week later, they notice that many of the sample means (sample size of 4) are above the upper control limit of 17.5 ounces. A reasonable assumption is that:

a. the system for weighing steaks is within acceptable limits

b. only random variation is present in the steak weighing process

c. the restaurant must have changed its guidelines for weighing steaks so that they can exceed customer expectations by delivering larger steaks

d. an attributable cause of variation is present in the steak weight process

e. none of the above