Question

The mean of a continuous data with number of terms is equal to 40 is 35 if 15 to 25 class with frequency 6 is added to the data find the new mean

Answer 1

Answer:

Class Interval Frequency cf

0−5 12 12

5−10 a 12+a

10−15 12 24+a

15−20 15 39+a

20−25 b 39+a+b

25−30 6 45+a+b

30−35 6 51+a+b

35−40 4 55+a+b=70

Here:

N=70

N/2=35

Median =16, Median class =15−20

So, I=15, h=5, f=15 and

xf=xf of preceding class i.e.24+a

We know,

Median =1+

⎩

⎪

⎪

⎪

⎨

⎪

⎪

⎪

⎧

h×

f

(

2

N

−cf)

⎭

⎪

⎪

⎪

⎬

⎪

⎪

⎪

⎫

Substitute all the value in the above formula, we get

16=15+{5×(35−24−a)/15}

⇒16=15+(11−a)/3

or a=8

Now, 70=55+a+b

70=55+8+b

⇒b=7

so, missing frequincies are 8 and 7.