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Question

What is the mean of the following distribution?
Marks1936606985
No. of Students6362591770

The correct answer is

52

Solution :- 

Calculating Mean from Marks and Frequency Data

To find the mean of a frequency distribution, we need to sum the product of each value (Marks) and its corresponding frequency (No. of Students) and then divide by the total number of observations (total frequency).

The formula for the mean ($\bar{x}$) of a frequency distribution is:

$$ \bar{x} = \frac{\sum (f \cdot x)}{\sum f} $$

Where:

  • $x$ represents the values (Marks).
  • $f$ represents the frequencies (No. of Students).
  • $\sum (f \cdot x)$ is the sum of the products of each value and its frequency.
  • $\sum f$ is the sum of all frequencies (total number of students).

Data Organization and Calculation

First, let's organize the given data into a table and calculate the product ($f \cdot x$) for each row:

Marks ($x$)No. of Students ($f$)Product ($f \cdot x$)
196$19 \times 6 = 114$
363$36 \times 3 = 108$
606$60 \times 6 = 360$
692$69 \times 2 = 138$
855$85 \times 5 = 425$


 

Summing the Values

Next, we calculate the sum of the 'No. of Students' column ($\sum f$) and the sum of the 'Product ($f \cdot x$)' column ($\sum (f \cdot x)$).

  • Total No. of Students ($\sum f$): $$ \sum f = 6 + 3 + 6 + 2 + 5 = 22 $$
  • Sum of Products ($\sum (f \cdot x)$): $$ \sum (f \cdot x) = 114 + 108 + 360 + 138 + 425 = 1145 $$

Mean Calculation

Finally, we apply the formula using the sums calculated above:

$$ \bar{x} = \frac{\sum (f \cdot x)}{\sum f} = \frac{1145}{22} $$

Performing the division:

$$ \bar{x} \approx 52.045 $$

Rounding the result to the nearest whole number, the mean marks are approximately 52.

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Important Questions from Measures of Central Tendency

  1. A random sample of 20 people is classified in the following table according to their ages:

    Age

    Frequency

    15 – 25

    2

    25 – 35

    4

    35 – 45

    6

    45 – 55

    5

    55 - 65

    3

    What is the mean age of this group of people?

  2. The median of the following observations 46, 64, 87, 41, 58, 77, 35, 90, 55, 92, 33 is 58. If 92 is replaced by 99 and 41 by 43 in the above data. The new median is:

  3. If the difference of mode and median is 36, then the difference of median and mean is:

  4. In a Mathematics test 15 students scored 80 marks, 20 students scored 75 marks, 28 students scored 65 marks and 25 students scored 60 marks, mode of the score is:

  5. If the mode of the scores 10, 12, 13, 15, 15, 13, 12, 10, x is 15, then what is the value of x?

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