Steel-reinforcing Bars. On the basis of extensive tests, the yield point

Steel-reinforcing Bars. On the basis of extensive tests, the yield point of a particular type of mild steel-reinforcing bar is known to be normally distributed with historical standard deviation 100. A random sample of 35 bars was taken and has a sample mean of 8439 lbs. Suppose that the specifications are that the yield point of a particular type of mild steel-reinforcing bar should be 8475 lbs.

(a) In constructing confidence intervals and hypothesis tests, would we use 2* or t* in this situation? Briefly explain why you would use one instead of the other.

(b) Estimate fi, the true mean yield point, with 95% confidence. Interpret.

(c) Suppose for the next sample, the bound is set at 15 lbs. Maintaining 95% confidence, what sample size will be required for the new sample?

 (d) Is there sufficient evidence that the mean yield point is less than the specifications call for the specs say 8475)? Conduct a hypothesis test, using the pvalue approach.

(e) State the kind of error could have been made in context of the problem.