Regression & Confidence Intervals

Worked: cylinder strengths

Sixteen cylinders average 4,200 psi with a sample standard deviation of 300 psi. For 95% confidence with 15 degrees of freedom, t = 2.131. The half-width is 2.131 × 300/√16 = 160 psi, so the interval is about 4,040 to 4,360 psi.