Strand bond performance of pre-stressed concrete. An experiment was carried out to investigate the strength of pre-stressed, bonded concrete after anchorage failure has occurred and the results published in Engineering Structures (June 2013). The maximum strand force, measured in kiloNewtons (kN), achieved after anchorage LO9 failure for 12 pre-stressed concrete strands is given in the accompanying table. Conduct a test of hypothesis to determine if the true standard deviation of the population of maximum strand forces is less than 5 kN. Test using a = .10.

158.2 161.5 166.5 158.4 159.9 161.9 162.8 161.2 160.1 175.6 168.8 163.7