Question

An engineer measured the Brinell hardness of 25 pieces of ductile iron that were subcritically annealed. The resulting data were:

170 167 174 179 179 187 179 183 179 156 163 156 187 156 167 156 174 170 183 179 174 179 170 159 187

The engineer hypothesized that the mean Brinell hardness of all such ductile iron pieces is greater than 165.

The engineer analyzed his data and calculated the following: The average Brinell hardness of the n = 25 pieces of ductile iron was 172.52 with a standard deviation of 10.31. (The standard error of the mean "SE Mean," calculated by dividing the standard deviation 10.31 by the square root of n = 25, is 2.06). The level of significance chosen by the engineer was 0.05. The population mean is unknown. Test the engineer’s hypothesis using either the critical value or p-value approach and conclude whether to reject or fail to reject the null hypothesis.

Answer 1