Mean Calculation:How to Find Mean?

CI	F
10-20	2
20-30.	3
30-40	1
40-50	2
50-60	2

What is the Mean of the above given frequency distribution table?

Solution :

C I.	Midpoint (X)	F	FX
10-20	15	2	30
20-30.	25	3	75
30-40	35	1	35
40-50	45	2	90
50-60	55	2	110
		⅀F=10	⅀FX=340

So Mean=⅀FX/⅀F

               =340/10

               =34

Notes: Here ⅀FX means sum of all the values of FX and ⅀F means sum of all the values of F

Mean Calculation 

How to Find Mean of a frequency distribution table in Deviation Method?

C I	F
4-8	2
8-12	3
12-16	2
16-20	1
20-24	3

Find the Mean of the above given frequency distribution table in deviation method?

Solution :

C I	F	MIDPOINT(X)	Y=X-A,A=14	FY
4-8	2	6	-8	-16
8-12	3	10	-4	-12
12-16	2	14	0	0
16-20	1	18	4	4
20-24	3	22	8	24

              ⅀F=11                                                            ⅀FY=0

Hence Mean= A+(⅀FY/⅀F)

                    =14+(0/11)

                    =14+0

                    =14

NOTES :Here A= initial point ,Y= deviation ,⅀FY means sum of all the values of FY and ⅀F means sum of all the values of F.

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