Question: In bridge construction, breaking tensile strength of materials used in construction is important. A sample of 25 alloy specimens were tested and the load at their failures measured in MPa are:

19.8, 18.5, 17.6, 16.7, 15.8, 15.4, 14.1, 13.6, 11.9, 11.4, 11.4, 8.8, 7.5, 15.4, 15.4, 19.5, 14.9, 12.7, 11.9, 11.4, 10.1, 7.9, 19.4, 15.3, 14.8

Assume that the data are normally distributed. Test at 5% level of significance the hypothesis that the mean failure strength of the material is 12 against that it is not.