question_answer

If the mean of the following frequency distribution is 65.6, find the missing frequencies

Class	Frequency
10-30 30-50 50-70 70-90 90-110 110-130	5 8 20 2
Total	50

 

Answer:

Let

Cl
10-30 30-50 50-70 70-90 90-110 110-130	20 40 60 80 100 120	5 8 20 2	-2 -1 0 1 2 3	-10 -8 0 20 6
		50		+8

Using step deviation method, Mean                                                              (1)                                         Also,