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Unformatted text preview: ENGR 4045U Quality Control Lecture 5 1 Lessons Learned Example of frequency distribution and histogram construction Normal distribution Definition of statistical inference Chi squared distribution Confidence interval Tdistribution 2 Schedule Week 3 Part III: Basic Methods of Statistical Process Control and Capability Analysis. Chapter 5: Methods and Philosophy of Statistical Process Control. Chapter 6: Control Charts for Variables. Week 4 Chapter 7: Control Charts for Attributes. Chapter 8: Process and Measurement System Capability Analysis. Week 5 Midterm1 3 Review What is Quality Methods for Quality Control Process, Product, Plant Modeling (IDEF0) Population / Sample PDSA/PDCA DMAIC Model Process Quality Statistical Methods, Mean, Variance, Standard Deviation, Median, Mode Histogram, Frequency Diagram Normal Distribution 4 Cumulative Normal Distribution The cumulative normal distribution is defined as the probability that the normal random variable x is less than or equal to some value (a) Where (.) is the cumulative distribution function of the standard normal distribution (mean = 0, standard deviation 1). 5 ) ( 2 1 ) ( 2 ) ( 2 1 a a z P a x P dx e a F a x P a x Example Tensile strength of paper used to make grocery bags is an important quality characteristic. It is known that the strength say, x is normal distribution with mean = 40 lb/in2 and standard deviation = 2 lb/in2, denoted x ~ N(40,2^2). The purchaser of the bags requires them to have a strength of at least 35 lb/in2. Calculate the probability that bags produced from this paper will meet or exceed the specifications. 6 Solution The probability that a bag produced from this paper will meet or exceed the specification is: P{x>=35}=1P{x<=35}=P{z<=(3540)/2} P{Z<=2.5}= (2.5)=0.0062 P{x>=35}=1P{x<=35}=10.0062=0.9938 7 Sampling from Normal Distribution X is a normal distribution with mean and variance 2....
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 Fall '10
 ahmadbarari
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