Answers within 1/1000 are considered correct due to rounding errors.

A sample of 30 beams have an average strength of 1908.8 lbs and s=327.1. What is the 95% confidence interval of the true population mean strength.

a. [1643.8, 1965.8]

b. [1638.9, 1797.8]

c. [1791.7, 2025.8]

d. None of the above

2. A key process indicator for a chemical process has the following values: 123, 106, 114, 128, 113, 109, 120, 102, 111. Assuming normality, what would be approximate 95% confidence interval of mean of this process.

a. [107.59, 120.41]

b. [121.43, 152.39]

c. [143.21, 153.54]

d. None of the above