Question

The National Institute of Standards and Technology (NIST) supplies "standard materials" whose physical properties are supposed to be known. For example, you can buy from NIST a copper sample whose melting point is certified to be 1084.80 degrees Celsius. Of course, no measurement is exactly correct. NIST knows the variability of its measurements very well, so it is quite realistic to assume that the population of all measurements of the same sample has the Normal distribution with mean LaTeX: \mu μ equal to the true melting point and standard deviation LaTeX: \sigma σ = 0.25 degrees Celsius. Here are six measurements on the same copper sample, which is supposed to have melting point 1084.80 degree Celsius: 1084.55, 1084.89, 1085.02, 1084.79, 1084.69, 1084.86 NIST wants to give the buyer of this copper sample a 90% confidence interval for its true melting point. What is this interval? Answer the following questions based on your work for exercise 16.6.

What z-score did you use to calculate the 90% confidence interval?

A) 1.645 B) 1.960    C) 2.576 I believe A is correct.  

What is the lower bound of the confidence interval?

A) 1084.33 B) 1084.63 C) 1084.93

What is the upper bound of the confidence interval?

A) 1085.27 B) 1084.97 C) 1084.67

Answer 1