FOR THE GROUPED DATA Ef (x - 1)2 N = N- 1 Efx2 (Efx)2 = N - 1 N ( N - 1)Salaries, Class Number In Pesos Mark fx X- u ( x-1)2 f (x - () 2 X2 fx2 300 - 399 12 400 - 499 17 500 - 599 20 600 - 699 25 700 - 799 17 800 - 899 12 900 - 999 10 1000 - 7 1099 TOTAL 120