500 câu trắc nghiệm Kinh tế lượng – 13B

5) A machine that is supposed to produce ball bearings with a diameter of 7 mm yields the
following data from a test of 5 ball bearings every 20 minutes.

Examine the given run chart or control chart and determine whether the process is within statistical control. If it is not, identify which of the three out-of-control criteria apply.
6) A control chart for \({\bar x}\) is shown below. Determine whether the process mean is within statistical control. If it is not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Process mean is not within statistical control. There are points above and below the control limits. There is an upward trend. There is a run of 8 values below the center line.
7) A control chart for R is shown below. Determine whether the process variation is within statistical control. If it is not, identify which of the three out-of-control criteria lead to rejection of statistically stable variation.

Process variation appears to be in statistical control.
8) A run chart for individual values is shown below. Does there appear to be a pattern suggesting that the process is not within statistical control? If so, describe the pattern.

Process appears to be out of statistical control. The variation is increasing over time.
9)

Process is out of statistical control. There is a downward trend.
Use the given process data to construct a control chart for p.
10) If the weight of cereal in a particular packet is less than 14 oz, the packet is considered nonconforming. Each week, the manufacturer randomly selects 1,000 cereal packets and determines the number that are nonconforming. The results for 12 consecutive weeks are shown below.
46 32 21 30 47 31 32 52 48 45 62 58


Solve the Problem.
11) An \({\bar x}\) chart based on standard deviations (instead of ranges) is made by plotting sample means with a centerline at \(\bar \bar x\) and control limits at \(\bar \bar x\) + A3\({\bar s}\) and \(\bar \bar x\) – A3\({\bar s}\) where A3 is found in Table 13-2 and \({\bar s}\) is the mean of the sample standard deviations. Construct an \({\bar x}\) chart based on standard deviations for the data below.
A manufacturer of high intensity video projector lightbulbs picks 6 lightbulbs at random each
day for quality control. The mean, standard deviation, and range (in hours) of the lifetimes of
the 6 lightbulbs are calculated. The results for 12 consecutive days are shown in the table below.