An engineer wants to know it the mean strengths of three different concrete mix

Question

An engineer wants to know it the mean strengths of three different concrete mix designs differ significantly. He randomly selects 9 cylinders that measure 6 inches in diameter and 12 inches in height in which A is poured, 9 cylinders of mixture B, and 9 cylinders of mixture C. After 28 days, he measures the strength (in pounds per square inch) of the cylinders. The results are presented in the accompanying table. (a) State the null and alternate hypotheses. Choose the correct answer below. A. H_0: at least one of the means is different H_1: mu_A = mu_B = mu_C B. H_0: mu_A = mu_B = mu_C and H_1: mu_A

Explanation / Answer

a) Correct Answer: Option (D)

b) Correct Answer: Option (B)

Descriptive Statistics: Mixture A, Mixture B, Mixture C

Total
Variable Count Mean StDev Variance Sum Sum of Squares
Mixture A 9 3960.0 106.7 11375.0 35640 141225400.0
Mixture B 9 4272 390 152244 38450 165484900
Mixture C 9 4025.6 195.8 38327.8 36230 146152500.0

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