3. points DevoreSt319 4 E040. My Notes Ask Your 3 An article suggested that yiel

Question

3. points DevoreSt319 4 E040. My Notes Ask Your 3 An article suggested that yield strength (ksi) for A36 grade steel is normally distributed with R-45 and 4.5. (a) What is the probability that yicld strength is at most 57 Grcater than 63 (Round your answers to four docimal places.) at most 39 greater than 63 (b) What Yield strength value separates the strongest 75% from the others? (Round your answer to three decimal places.) ksI You may need to use the appropriate table in the Appendix of Tables to ansiwer this question Need Help?

Explanation / Answer

Mean is 45 and sd is 4.5

a) P(x<39) =P(z<(39-45)/4.5)=P(z<-1.33) or 1-P(z<1.33)

from normal distribution table we get 1-0.9082 =0.0918

P(x>63) =P(z>(63-45)/4.5)=P(z>4)=0 (because z above 3 gives pobability almost 0)

b) strongest 75% means we need to find a value which is above 75% the smallest value. for p=0.75, we see that z value is 0.68

thus, 45+0.68*4.5 =48.06

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