Question

A sample of 18 joint specimens of a particular type gave a sample mean proportional limit stress of 8.45 MPa and a sample standard deviation of 0.77 MPa. (a) Calculate and interpret a 95% lower confidence bound for the true average proportional limit stress of all such joints. (Round your answer to two decimal places.) MPa Interpret this bound. O with 95% confidence, we can say that the value of the true mean proportional limit stress of all such joints is less than this value. | O with 95% confidence, we can say that the value of the true mean proportional limit stress of all such joints is greater than this value. O with 95% confidence, we can say that the value of the true mean proportional limit stress of all such joints is centered around this value. What, if any, assumptions did you make about the distribution of proportional limit stress? We must assume that the sample observations were taken from a uniformly distributed population. O We must assume that the sample observations were taken from a chi-square distributed population O We must assume that the sample observations were taken from a normally distributed population. We do not need to make any assumptions ess of a s ejo t of this type (Round your answer to two decr al places.) (D Calculate and interpreta 95% lower prediction bound or proportional lin its MPa

Answer 1

X-8.45 o 0.77 n-18 df n-1-18-1 -17 For 95% confidence, the value of ta/2-2.11 8.45 2.11 x 0.77/V18 8.45 0.382945 -8.45-0.382945 to 8.45+0.382945 -8.07 to 8.83 So, lower confidence interval is 8.07