A newspaper article reported on differences between unemployment rates of U. S. military veterans and non-veterans. Data selected randomly from local veterans and non-veterans, shows a 1% difference. Sample sizes were large enough to give a P-value of 0.015. What issue exists in concluding that the unemployment rate is significantly higher for U. S. veterans? a. A 1% difference is not statistically significant.
b. The samples gathered cannot be expected to represent the larger populations of U. S. veterans and non-veterans.
c. The samples were self-selected.
d. The groups were not chosen by random assignment.