A19. Adam Shapiro, Director of Human Resources, is exploring employee absenteeism at the Vivaldi (population 1) and the Beethoven (population 2) Piano Factories. Previous studies indicate no difference in employee absenteeism at the two factories. (The mean number of days absent per employee was the same at each factory.) Adam plans to test this hypothesis using a random sample of 49 employees from each factory. His null hypothesis is a. u 1 - 1 2 0 b. u 1 - u 220 C. u 1 - u 2=0 d. u 1 - u 250