The score in Maths of 50 students of a class is given in the following table. Calculate the mean score.

Interval  Frequencies
0-10 2
10-20 11
20-30 28
30-40 6
40-50 3

This question was previously asked in
SSC CHSL 2021 (Held On : 31 May 2022 Shift 1)
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  1. 28.8
  2. 22.2
  3. 24.4
  4. 26.6

Answer (Detailed Solution Below)

Option 3 : 24.4
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SSC CHSL Exam 2023 Tier-I Official Paper (Held On: 02 Aug 2023 Shift 1)
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Detailed Solution

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Given:

Total number of students = 50

Interval  Frequencies
0-10 2
10-20 11
20-30 28
30-40 6
40-50 3

Concept Used:

Mean = Total Sum of f(x) ÷ Total Sum of f

Calculation:

⇒ Firstly for each interval, we will find the midpoint of it.

⇒ For interval 0-10, Midpoint = \(\frac{0+10}{2}\) = 5

⇒ For interval 10-20, Midpoint = \(\frac{10+20}{2}\) = 15

Interval Frequencies (f) Midpoint (x)
0-10 2 5
10-20 11 15
20-30 28 25
30-40 6 35
40-50 3 45
Total 50 125

⇒ Now, to calculate the values of f(x), multiply each midpoint with their respective frequencies.

Interval Frequencies (f) Midpoint (x) f(x)
0-10 2 5 10
10-20 11 15 165
20-30 28 25 700
30-40 6 35 210
40-50 3 45 135
Total 50 125 1220

⇒ So, Mean = \(\frac{\sum f(x)}{\sum f}\)

⇒ Mean = \(\frac{1220}{50}\) =24.4

Hence, the mean score of the students is 24.4.

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