Q18) Concrete placed on a structure was subsequently cored after 28 days, and the flowing results were obtained of the c

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Q18 Concrete Placed On A Structure Was Subsequently Cored After 28 Days And The Flowing Results Were Obtained Of The C 1 (102.86 KiB) Viewed 71 times

Q18) Concrete placed on a structure was subsequently cored after 28 days, and the flowing results were obtained of the compressive strengths from the five test specimens: 28.56, 23.48, 23.45, 27.85, 23.25 MPa (a) Determine the 90% two-sided confidence interval of the mean concrete strength (b) Suppose the confidence interval established in part (a) is too wide, and the engineer would like to have a confidence interval to be +2 MPa of the computed sample mean concrete strength. Generally, more specimens of concrete would be needed to keep the same confidence level. However, without additional samples, what is the confidence level associated with the specified interval based on the five measurements given above? (e) If the required minimum compressive strength is 24 MPa, perform a one-side hypothesis test at the 2% significance level.