contractor claims that the mean compressive strength for a concrete mix is 5000 psi (μ) and that it has a standard deviation of 400 psi (σ). If you break 20 cylinders (N) and obtain a mean compressive strength of 4,800 psi (m), would you believe the contractor’s claim? Why? (Hint; Use statistical t-test.) Next, what is the maximum number of breaks (N) that could be performed that WOULD make you believe the contractor’s claim? Assume that the results wouldn’t change, i.e. σ = 400 psi and m = 4,800 psi. Recall that the
A contractor claims that the mean compressive strength for a concrete mix is 5000 psi (μ) and that it has a standard deviation of 400 psi (σ). If you break 20 cylinders (N) and obtain a mean compressive strength of 4,800 psi (m), would you believe the contractor’s claim? Why? (Hint; Use statistical t-test.) Next, what is the maximum number of breaks (N) that could be performed that WOULD make you believe the contractor’s claim? Assume that the results wouldn’t change, i.e. σ = 400 psi and m = 4,800 psi. Recall that the equation to find the lower bound of a one sided distribution is LB = μ - (tσ)* σ/(N^0.5) Because the sample size is relatively small, use the ‘student t test’ to represent the
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