Insulation workers. Twenty-six cancer deaths were observed in a cohort of 556 insulation workers. Based on national statistics, a cohort of this size and age distribution was expected to experience 14.4 incident cases during the observation period. Therefore, under the null hypothesis, p = p0 = 14.4/556 = 0.02590. Test whether the observed incidence is significantly greater than expected. Show all hypothesis-testing steps.