Answer:
This value of 5675 psi by the contractor is safer than 5487.5 psi as it is of lesser value.
Step-by-step explanation:
The following parameters are given from the question above. These information is used in solving this problem.
=> The mean value of his compression test = 6500 psi, the standard deviation = 500 psi, the average of the mean = 5900 psi and the number of sample measurements = 8.
The first thing to do right now is to determine the characteristic strength, this can be calculated as below:
Characteristic strength= average of the mean - (1.65/2) × standard deviation.
Characteristic strength = 5900 - (0.825) × 500 = 5487.5 psi.
The next thing to do is to Determine the target mean strength.
Target mean strength = 5487.5 psi + 1.65 × 500 = 6312.5 psi.
The above is from taking samples from 8 samples.
Now, let's consider the characteristic strength by the contractor.
Characteristics strength = 6500 - 165 × 500 = 5675 psi.
This value of 5675 psi by the contractor is safer than 5487.5 psi as it is of lesser value.
