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Tài liệu tiếng Anh Session 4 chapter 5 Managing quality, dành cho cao học.
05 - 01 05 - 02 • • • !" • #$" 05 - 03 # • %& ' • ! • ( • )* 05 -04 ) 05- 05 ) & + • +' • , • "- • + • ! 05 - 06 #! • • ) – ## – . – +. – +. 05 - 07 ! • /0 • . • (+ 05 - 08 +$+ 05 - 09 +$+ 1$22 $00 +$+ 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4/5 4/5 6 7 3 3 3 3 3 3 3 3 3 05- 10 [...]... LCLx = x – A2R 05 - 32 Calculating Control Chart Factors 05 - 33 Steps for x- and R-Charts 1 2 3 4 Collect data Compute the range Use Table 5. 1 to determine R-chart control limits Plot the sample ranges If all are in control, proceed to step 5 Otherwise, find the assignable causes, correct them, and return to step 1 5 Calculate x for each sample 05- 34 Steps for x- and R-Charts 6 Use Table 5. 1 to determine... control chart 1 2 3 4 Random sample Plot statistics Eliminate the cause, incorporate improvements Repeat the procedure 05 - 23 Control Limits and Sampling Distribution UCL Nominal LCL Assignable causes likely 1 2 3 Samples 05- 24 Control Charts Variations UCL Nominal LCL Sample number (a) Normal – No action 05- 25 Control Charts Variations UCL Nominal LCL Sample number (b) Run – Take action 05- 26 Control... Monitor 05- 27 Control Charts Variations UCL Nominal LCL Sample number (d) Exceeds control limits – Take action 05- 28 Control Chart Errors Type I error – Type II error – Concluding that a process is out of control Concluding that a process is in control when it is out of control when it is in control 05 - 29 Control Chart Types • 05 - 30 Variable Control Charts R-Chart UCLR = D4R and LCLR = D3R 05 - 31... correct them, and return to step 1 05- 35 Example 5. 1 The management of West Allis Industries is concerned about the production of a special metal screw used by several of the company’s largest customers The diameter of the screw is critical to the customers Data from five samples appear in the accompanying table The sample size is 4 Is the process in statistical control? 05 - 36 ... deviation of a sample xi = observation of a quality characteristic (such as time) n = total number of observations x = mean 05 - 17 n 2 Sampling Statistics 1 The sample mean is the sum of the observations divided by the total number of observations n x= ∑x i =1 i n where xi = observation of a quality characteristic (such as time) n = total number of observations x = mean 05 - 18 Sampling Statistics 2 The range... − 2 i (∑ x ) i n −1 where σ = standard deviation of a sample 05 - 19 n 2 Sampling Distribution 05 - 20 Types of Variation • Common cause – Variation that is random, unidentifiable and unavoidable • Assignable cause – Variation that can be identified and eliminated 05 - 21 Effects of Assignable Cause Variation on the Process Distribution 05 - 22 Control Charts • Time-ordered diagram used to determine... Inspection – Inspect each product at each stage 05 - 15 Sampling Statistics Sample Mean Sample Range Sum of the observations divided by the total Difference between the largest and observations smallest observation in a sample n where x = ∑x i =1 i n xi = observation of a quality characteristic (such as time) n = total number of observations x = mean 05 - 16 Sampling Statistics Standard deviation– The... fan blades TARGET: Firm A’s specs Yes Accept No blades? 05- 13 Statistical Process Control (SPC) • SPC • Performance Measurements The application of statistical techniques to determine whether a process is delivering what the customer wants – Variables - Characteristics that can be measured – Attributes - Characteristics that can be counted 05 - 14 Sampling • Sampling Plan – Size of the sample – Time... Black Belts • Green Belts 05 - 11 Acceptance Sampling • Acceptance Sampling • Acceptable Quality Level – The application of statistical techniques to determine if a quantity of material from a supplier should be accepted or rejected based on the inspection or test of one or more samples – A statement of the proportion of defective items that the buyer will accept in a shipment 05 - 12 Acceptance Sampling . 4/ 5 4/ 5 6 7 3 3 3 3 3 3 3 3 3 05- 10 +$+! 05. 03 # • %& ' • ! • ( • )* 05 - 04 ) 05- 05 ) & + • +' • , • "- • + • . – +0 – ) – (8 • ! – ! 05 - 15 ++ + + 05 - 16 n x x n i i ∑ = = 1 x i B&?@ n