=+21. The article “Ultimate Load Capacities of Expansion Anchor Bolts” (J. of Energy Engr., 1993:

139–158) gave the following summary data on shear strength (kip) for a sample of 3y8-in. anchor bolts: n 5 78, x 5 4.25, s 5 1.30. Calculate a lower confidence bound using a confidence level of 90%

for true average shear strength.