Statistic summary for quality engineering-2, Lecture notes of Quality Management

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IE8406 Quality Engineering Practice 2

28.02.2024 1E8406 Quality Engineering Practice 2 3.33. A random sample of 50 units is drawn from a pro- duction process every half hour. The fraction of non- conforming product manufactured is 0.02. What is the probability that p < 0.04 if the fraction noncon- forming really is 0.027 4.2. The tensile strength of a fiber used in manufacturing cloth is of interest to the purchaser. Previous experi- ence indicates that the standard deviation of tensile strength is 2 psi. A random sample of eight fiber specimens is selected, and the average tensile strength is found to be 127 psi. (a) Test the hypothesis that the mean tensile strength equals 125 psi versus the alternative that the mean exceeds 125 psi. Use a = 0.05. (b) What is the P-value for this test? (c) Discuss why a one-sided alternative was chosen in part (a). (d) Construct a 95% lower confidence interval on the mean tensile strenpth. 4.3. The service life of a battery used in a cardiac pace- maker is assumed to be normally distributed. A ran- dom sample of 10 batteries is subjected to an accel- erated life test by running them continuously at an elevated temperature until failure, and the following lifetimes (in hours) are obtained: 25.5, 26.1, 26.8. 23.2, 24.2, 28.4, 25.0, 27.8, 27.3, and 25.7. (a) The manufacturer wants to be certain that the mean battery life exceeds 25 h. Whal conclusions can be drawn from these data (use a = 0.05)? (b) Construct a 90% two-sided confidence interval on mean life in the accelerated test. (c) Construct a normal probability plot of the battery life data. What conclusions can you draw?