STATISTICS 1

In Biology test the following marks were recorded.

marks	10-19	20-29	30-39	40-49	50-59
No. of students	2	4	5	6	3

Calculate the mean.

Solution

In this question we are going to apply the method of assumed mean.

Here you are required to produce the frequency distribution table.

Let us take 44.5 as our assumed mean(A). Take away the assumed mean from each class mark. 

Class interval	Class mark (x)	d=x-A	Frequency (f)	fx	fd
10-19	14.5	-30	2	435	-60
20-29	24.5	-20	4	98	-80
30-39	34.5	-10	5	150	-50
40-49	44.5	0	6	267	0
50-59	54.5	10	3	163.5	30
			∑f = 20	∑fx = 730	∑fd = -160

Mean = A +  ∑fd

                      ∑f

Mean = 44.5 + ( -160)

                            20

Mean = 44.5 -  8

                           

         

Hence Mean =  36.5

TRY THIS………….

In Civics test the following marks were recorded.

marks	10-14	15-19	20-24	25-29	30-34
No. of students	4	8	10	12	6

Given assumed mean of 27, find the mean.