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Examoogle • User • info@examoogle.com • EE-2024-8821
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The mean marks of the following distribution is:
| Marks Obtained | No. of Students |
|---|---|
| 28 | 8 |
| 12 | 12 |
| 57 | 18 |
| 85 | 13 |
49
53
39
43
49
Use the deviation method: assume a mean (e.g., 50), calculate the deviations, find their weighted mean, and add it back to the assumed mean to simplify multiplication.
Marks obtained (xi): 28, 12, 57, 85; Number of students (fi): 8, 12, 18, 13.
Mean(x)=∑fi∑fixi
Use the deviation method: assume a mean (e.g., 50), calculate the deviations, find their weighted mean, and add it back to the assumed mean to simplify multiplication.
Careless addition of the frequencies or multiplication errors in the product table (sumfixi).
Calculate sum of frequencies (sumfi)
Sum the number of students: 8+12+18+13=51.
∑fi=51
Calculate products (fi×xi)
Multiply each mark by the corresponding number of students: (28×8)=224, (12×12)=144, (57×18)=1026, (85×13)=1105.
224+144+1026+1105=2499
Calculate Mean
Divide the total sum of marks by the total number of students: 512499.
x=512499=49
A is correct because the calculated mean 512499 equals 49.
This is a standard statistical measure problem often seen in RRB/SSC exams; always double-check the arithmetic of the product sum ∑fixi as it is the most likely place for a calculation error.
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