I already got the answerbut i am not satisfied ..plz give a clear and well expla
ID: 3205403 • Letter: I
Question
I already got the answerbut i am not satisfied ..plz give a clear and well explained answer
The compressive strength of concrete delivered by a supplier can be modeled by a lognormal random variable. Its mean and the coefficient of variation are estimated to be 4.7 ksi and 0.21, respectively. If the 10^th percentile value is the design value, calculate the value of the compressive strength to be used in a design. Suppose the COV of the compressive strength is reduced to 0.10 without affecting its mean value by introducing quality control procedures. Calculate the design value of the compressive strength if it is assumed to be the 10^th percentile value. By comparing the results obtained in Parts (a) and (b), discuss whether quality control measures are preferable.Explanation / Answer
ANSWER :-
The compressive strength of concrete delivered by a supplier can be modeled by a lognormal random variable. Its mean and the coefficient of variation are estimated to be 4.7 ksi and 0.21, respectively.
(a)
(b)
The 10th percentile value is e4.7-1.282*0.10 ksi =96.7180 ksi
(c)
Higher strength is always preferable in the compressive strength of concrete. Now in 2nd case the 10th percentile value is higher than the 1st case’s 10th percentile value. Therefore the comparison of the results obtained in Parts (a) and (b) indicates that quality control measures are preferable as it is increasing the quality and strength of the concrete.
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