1.

Find the mean of the following frequency distribution:Classes:               0-20         20-40                            40-60       60-80                            80-100Frequency:          15            18                            21            29                            17

Answer» `x_i = 10, 30, 50, 70, 90`
`f_i = 15 , 18 , 21, 29, 17`
`A= 50, L=20`
`d_i= -40, -20, 0 , 20, 40`
`u_i= (d_i-h)= -2, -1, 0 , 1 ,2`
`f_i*u_i= -30, -18, 0 ,29, 34 `
`sum(f_i*u_i) = 15`
`sumf_i = N= 100`
`Mean= A + h*((sumf_i*u_i)/N)`
`= 50 + 20*(15/100)`
`= 50+3 = 53`


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