The nominal shear strength in kN for a sample of 15 prestre

The nominal shear strength , in kN, for a sample of 15 prestressed content beams are as follows: 580400428825850875920550 57575063636059073535950 What is the 99% confidence interval for the mean shear strength? A stress analysis was conducted on random sample of epoxy-bonded joints from two species of wood. A random sample of 120 joints from species A had a mean shear stress of 1250 psi and a standard deviations of 350 psi; a random sample of 95% confidence interval for the difference in mean shear stress between the two species.

Solution

From the observations above

Mean= 668.26667

Standard Error=192.089/2.873= 49.59

CI= Mean +/- (z-value)SE = 668.26667+/- 2.575(49.59)

At 99% CI the z-value for two tailed test is 2.575

CI=540.55167,795.9821