Question

If UI=xi-25/10, sigma fiui=20, sigma fi=100, then mean=¿

Answer 1

The mean = 27

• We know that, mean by step deviation method is given by

                  $Mean=A+h\frac{sigma(f_{i}u_{i})}{sigma(f_{i})}--------(1)$

• Given

               $u_{i}=\frac{x_{i}-25}{10}$

• Comparing with

               $u_{i}=\frac{x_{i}-A}{h}$

        we get

              A = 25, h = 10

• Also

              $sigma(f_{i}u_{i})=20,sigma(f_{i})=100$

• Substituting above values in (1)

               $Mean=25+10(\frac{20}{100})$

               Mean = 25 + 2

              Mean = 27