Tests performed w ith unequal sample sizesĬomments  Spec is +/- 50. MSA: X-BAR / S CHART OUTPUT Xbar-S Chart of Actual Measurement by Facility DHM 1 Calibration Part per Facilityģ Facilities Sorted by Facility Date & Time Multiple Measurements per Day on most Days. A good measurement system will be incontrol for each individual Part. A good measurement system will be in-control  Xbar Chart: Displays any Drift over time in the average measurements. VARIATION S Chart: Displays the Measurement Error. GATHERING DATA  Need Multiple measurements per time period  Can use 1 or more Parts  Need a minimum of 10 subgroups large parts having more or less measurement error than small parts) Limitation  Will NOT detect measurement that varies by nominal value (e.g. MINITAB EXERCISE – I-MR CHARTS I-MR Chart of Glucoselevel by SubjectIDĪdvantages  Pictorial look at MSA results  Measurement error can easily be calculated  O Sort Data: Sort the data by SubjectID & Reading What do the Charts tell us? We need to look at the individual people. MINITAB EXERCISE - XBAR / S CHARTS OUTPUT Xbar-S Chart of Glucoselevel U C L=130.72 XBAR-S CHARTS: STAT > CONTROL CHARTS > VARIABLES CHARTS FOR SUBGROUPS > XBAR-S Open worksheet GATHERING DATA  Define rational basis for subgrouping  An S-Chart is typically used when the subgroup’s sample size is > 9  Select sampling frequency  Need a minimum of 10 subgroups VARIATION Short Term: Measures the variation within the Subgroups based on the subgroup stddev (S chart)  Long Term: Measures the variation between the Subgroups based on the subgroup average (X Bar chart)  They represent the range of the subgroup averages. Limitation The Xbar Chart control limits do not represent the overall data range.  Also, the center line of the S-Chart provides a good estimate for the data’s standard deviation. MINITAB EXERCISE - XBAR / R CHARTS Xbar-R Chart of Lengths by Supplier S upp1Īdvantages  Very sensitive to changes in data. O Stack Data: Stack the 2 Suppliers so the data can be looked at together on the same chart What do the Charts tell us? We need to look at the individual suppliers. MINITAB EXERCISE - XBAR / R CHARTS OUTPUT Xbar-R Chart of Length XBAR-R CHARTS: STAT > CONTROL CHARTS > VARIABLES CHARTS FOR SUBGROUPS > XBAR-R Open worksheet GATHERING DATA  Define rational basis for subgrouping  Select sample size for the subgroups  Select sampling frequency  Need a minimum of 10 subgroups VARIATION Short Term: Measures the variation within the Subgroups based on the subgroup range (Range chart)  Long Term: Measures the variation between the Subgroups based on the subgroup average (X Bar chart)  MINITAB EXERCISE INDIVIDUALS / MOVING RANGE OUTPUT I-MR Chart of Weight by Group 1Īdvantages Sensitive to changes in data Limitation Unlike the Individual Chart, the Xbar Chart control limits do not represent the overall data range. MINITAB EXERCISE INDIVIDUALS / MOVING RANGE OUTPUT MINITAB EXERCISE INDIVIDUALS / MOVING RANGE OUTPUT I-MR Chart of Weight 1050 I / MR CHART: STAT > CONTROL CHARTS > RUN CHART I-MR Chart analyzes individual data over time. I / MR CHART: STAT > CONTROL CHARTS > I-MR  Need a minimum of 10 data points Variation  Short Term: Measures relatively rapid changes over time (Moving Range chart)  Long Term: Measures relatively gradual changes over time(Individuals chart) Do NOT use P-Charts if the values are 100 since it violates basic P-Chart assumptions.

Use:  When only have 1 measurement per time period  When want to chart Counts. SPC & MSA Using Minitab I Chart for C1 39ĪGENDA Continuous & Attribute Data  IMR Charts  Xbar & R Charts  Xbar & S Charts MSAs  Using Xbar & S Charts for MSAs  Non-Destructive Variable MSAs (NOTE: Minitab will also Analyze Destructive Variable MSAs & Attribute MSAs)Ĭontrol Limits are NOT Spec Limits UCL Plotted Data Center LineĭATA PLOTTED OVER TIME UCL = Upper Control LimitĬONTROL CHARTS INDIVIDUAL /MOVING RANGE 

Xbar chart minitab