Question

.
The following table gives the marks obtained by the students in a test:
ga
Marks
Below 10
Below 20
Below 30
Below 40
Below 50
No. of
4
9
11
25
30
students
What is the mean marks of the students? (correct to one decimal place)​

Answer 1

Answer:

25

Step-by-step explanation:

25 is the mean of this question

write that in assending or dessending order and divided by the the number given

Answer 2

Answer:

Answer

Here we have, cumulative frequency distribution less than type. First we convert it into an ordinary frequency distribution. We observe that the number of students getting marks less than 10 is 5 and 9 students have secured marks less than 20. Therefore, number of students getting marks between 10 and 20 ( inclusive 0 and exclusive 10) is 9−5=4. Similarly, the number of students getting marks between 20 and 30 is 17−9=8 and so on. Thus, we have the following distribution frequency distribution:

Marks: 0−10 10−20 20−30 30−40 40−50 50−60 60−70 70−80 80−90 90−100

Number of students: 5 4 8 12 16 15 10 8 5 2

Let us Let us now compute arithmetic mean by taking 55 and the assumed mean.

Computation of Mean

Marks Mid-value Frequency u

i

10

x

i

−55

f

i

u

i

0−10 5 5 −5 −25

10−20 10 4 −4 −16

20−30 25 8 −3 −24

30−40 35 12 −2 −24

40−50 45 16 −1 −16

50−60 55 15 0 0

60−70 65 10 1 10

70−80 75 8 2 16

80−90 85 5 3 15

90−100 95 2 4 8

Total N=∑f

i

=85 ∑f

i

u

i

=−56

We have,

N=N=∑f

i

=85,∑f

i

u

i

=−56,h=10andA=55

∴

X

=A+h(

N

1

∑f

i

u

i

)

⇒

X

=55+10×

85

−56

=55−6.59=48.41Marks.

Hence, mean marks scored by the students = 48.41.