Six Sigma Control Charts

This chart illustrates a data trend known as freaks. Which correctly actions would you take to solve the problem exhibited in this control chart?

*Determine if inspections should be performed differently or occur more frequently *Verify testing procedures

Which statements accurately describe basic concepts related to control charts?

*Special cause variations may show as data points outside the control limits on a control chart *Control charts are used to monitor and analyze process variations *Issues related to manpower, measures, and methods are among the main causes of variations

Xbar-s

*Subgroups are greater than ten *Standard deviation is a better measure of dispersion for relatively large data samples

An airline reduced excessive variability in passenger processing time. To monitor the new process, they conduct five observations per hour for 20 hours. Which statements correctly interpret the chart?

*Test 1 failed *Test 2 failed *There is special cause variation evident in the control chart

You're testing wire that requires a tensile strength of over 200 pounds. You've tracked defects in a random sample of wire segments for 20 days. Which statements correctly interpret the np chart?

*Test 1 failed *There is special cause variation shown

Xbar-R

*The subgroup size is fixed *Subgroup have two to ten data points

You're monitoring employee injuries in a factory. The subgroup size is constant, and the number of injuries occurring is small. Which statement correctly interpret the c chart you create?

*There is no special cause variation *The process is in control

You've created an ImR chart to determine if there are non-normal variations in the daily transportation expenses of an event management company. Which statements correctly interpret the chart?

*There is no special cause variation shown in the I chart *Test 1 failed in the MR chart

Every month for ten months, you sample telemarketing calls and record the total number of errors in each call. Which statements correctly interpret the u chart you create to track this?

*There is special cause variation *Test 1 failed

You've create a p chart for a large telecom company project to determine the proportion of buyers who buy their $50 wireless plan. Which statement correctly interpret the chart?

*There is special cause variation present in the data *Test 1 failed

Center line

*Xdoublebar

Process shift

A run of 12 data points in a row, all above the mean

Process shift

A run of 15 data points in a row that all appear below the center line

Systematic variation

A run of 16 data points in a row that alternate up and down

systematic variation

A run of 18 data points that follow an alternating up-and-down pattern

Stratification

A run of 20 data points in a row, all clustered around the center line

Process drift

A run of ten data points in a row that start at the mean and advance toward the UCL

Freaks

All data points are within the control limits except for one that dips below the LCL

Recurring cycles

Data points showing values that re close to the UCL at the same time each day

Step 5

Analyze and interpret the chart to take corrective actions, if necessary

Step 2

Connect the points

Step 3

Draw the center line

Step 4

Draw the upper and lower control limits

Step 1

Plot the data points on a chart

UCL

Xdoublebar + (A3 x sbar)

LCL

Xdoublebar - (A3 x sbar)

Median

Your process does not have a perfectly normal distribution

You sample 100 items daily for 20 days. What type of control chart should you use to examine the variability in your process by the number of defective units the process produces on a given day?

np