STATISTICS 1

In Civics test the following marks were recorded.

marks	10-19	20-29	30-39	40-49	50-59	60-69	70-79
No. of students	4	5	7	9	6	5	4

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 54.5 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	-40	4	58	-160
20-29	24.5	-30	5	122.5	-150
30-39	34.5	-20	7	241.5	-140
40-49	44.5	-10	9	400.5	-90
50-59	54.5	0	6	327	0
60-69	64.5	10	5	322.5	50
70-79	74.5	20	4	298	80
			∑f = 40	∑fx = 1770	∑fd = -410

Mean = A +  ∑fd

                       ∑f

Mean = 54.5 +  -410

                             40

Mean = 54.5 +  (-10.25)

                    

Mean = 44.25       

         

Hence Mean =  44.25

TRY THIS………..

In Civics test the following marks were recorded.

marks	10-14	15-19	20-24	25-29	30-34	35-39	40-44
No. of students	4	5	7	9	6	5	4