Question

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The following observations were made cn fracture toughness of a base plate of 18 % nickel maraging steel (in ksi in.. given in increasing order)]: 65.4 71.9 72.8 73.1.2 73.5 75.5 75.7 75.8 76.1 76.2 76.2 77.0 77.9 78.1 79.6 79.7 79.9 80.1 82.2 83.5 93.8 Calculate a 99% CI for the standard deviation of the fracture toughness distribution. (Round your answers to one decimal place.) ksi Vin Is this interval valid whatever the nature of the distribution? Explain. O The distribution needs to be approximately normal. O The distribution needs to be approximately uniform. O The distribution needs to be skewed to the right. O The interval is always valid. You may need to use the appropriate table in the Appendix of Tables to answer this question.

Answer 1

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A B C G H F change the value highlighted in 5.40 99 % 22 65.4 76.2 71.9 77.0 72.8 77.9 73.1 78.1 73.2 79.6 73.5 79.7 75.5 79.9 75.7 80.1 75.8 82.2 76.1 83.5 76.2 93.8 Sample standard deviation (s) Confidence level (C) Sample size (n) Degrees of freedom (df) Area to the right of XL Area to the right of XŘ 21 0.995 0.005 x 8.034 41.401 12. 15 16 17 Confidence interval for population standard deviation: 3.8 to 8.7 (3.8, 8.7) ksi vin The distribution needs to be approximately normal.