STATISTICS B1

In French test the following marks were recorded.

marks	30-34	35-39	40-44	45-49	50-54	55-59	60-64	65-69
No. of students	4	5	6	7	10	9	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 42 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
30-34	32	-10	4	128	-40
35-39	37	-5	5	185	-25
40-44	42	0	6	252	0
45-49	47	5	7	329	35
50-54	52	10	10	520	100
55-59	57	15	9	513	135
60-64	62	20	5	310	100
65-69	67	25	4	248	100
			∑f = 50	∑fx = 2485	∑fd = 405

Mean = A +  ∑fd

                       ∑f

Mean = 42 +  405

                          50

Mean = 42 +  (8.1)

                    

Mean = 50.1

         

Hence Mean =  50.1