Topic 5 Quiz
The number of defects after a hotel room cleaning (sheets not straight, smears on mirror, missed debris on carpet, etc) should be measured using what type of control chart?
c-chart
The results of inspection of DNA samples taken over the past 10 days are given below. Sample size is 100. Day: 1 2 3 4 5 6 7 8 9 10 Defectives: 7 9 9 11 7 8 0 11 13 2 Give the upper and lower 3-sigma control chart limits. Given the limits, is the process in control for the following days? Day: 11 12 13 # of Defects: 8 11 13
UCLp = 0.157 LCLp = 0 Day: 11 - yes 12 - yes 13 - yes
The purpose of an x-bar chart is to determine whether there has been a:
change in the central tendency of the process output.
The c-chart signals whether there has been a:
change in the number of defects per unit.
Statistical process control charts:
display upper and lower limits for process variables or attributes and signal when a process is no longer in control.
Ten samples of a process measuring the number of returns per 100 receipts were taken for a local retail store. The number of returns were 10, 9, 11, 7, 3, 12, 8, 4, 6, and 11. Find the standard deviation of the sampling distribution for the p-bar chart.
.0273
A manager wishes to build a 3-sigma range chart for a process. The sample size is five, the mean of sample means is 16.01, and the average range is 5.3. From Table S6.1, the appropriate value of D3 is 0, and D4 is 2.115. What are the UCL and LCL, respectively, for this range chart?
11.2 and 0
Red Top Cab Company receives multiple complaints per day about driver behavior. Over 9 days the owner recorded the number of calls to be 3, 0, 8, 9, 6, 7, 4, 9, and 8. What is the upper control limit for the 3-sigma c-chart?
13.35
Which of the following is true of a p-chart?
The lower control limit may be at zero
Assignable causes:
are causes of variation that can be identified and investigated.
Natural variations:
are the many sources of variation that occur when a process is under control. when grouped, form a pattern, or distribution. affect almost every production process. are tolerated, within limits, when a process is under control. **All of the above are true.
To set x-bar chart upper and lower control limits, one must know the process central line, which is the:
average of the sample means
Control charts for variables are based on data that come from:
averages of small samples.
The number of late insurance claim payouts per 100 should be measured with what type of control chart?
p-chart
Auto pistons at Wemming Chung's plant in Shanghai are produced in a forging process, and the diameter is a critical factor that must be controlled. From sample sizes of 10 pistons produced each day, the mean and the range of this diameter have been as follows: Day: 1 2 3 4 5 Mean x-bar (mm): 154.9 153.2 155.6 157.5 156.6 Range R (mm): 4.0 4.6 4.1 5.0 4.7 What is the value of x-bar-bar? What is the value of R-bar? What are the UCLx and LCLx using 3-sigma? What are the UCLR and LCLR using 3-sigma?
x-bar-bar = 155.96mm R-bar = 4.52mm UCLx-bar = 157.35mm LCLx-bar = 154.57mm UCLR = 8.03mm LCLR = 1mm
