Question:

The average weight of $25$ boys was calculated to be $78.4\, kg$. It was later discovered that one weight was misread as $69$ kg instead of $96 \,kg$. The correct average is

Updated On: Jun 23, 2023
  • $79\, kg$
  • $79.48 \,kg$
  • $81.32 \,kg$
  • $80.04 \,kg$
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The Correct Option is B

Solution and Explanation

Incorrect sum of all items $= 78.4 \times 25 = 1960\, kg$ $\therefore$ Correct sum $= 1960 - 69 + 96 = 1987 \,kg$ $\therefore$ Correct average $= \frac{1987}{25} = 79.48\,kg$.
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Concepts Used:

Mean Deviation

A statistical measure that is used to calculate the average deviation from the mean value of the given data set is called the mean deviation.

The Formula for Mean Deviation:

The mean deviation for the given data set is calculated as:

Mean Deviation = [Σ |X – µ|]/N

Where, 

  • Σ represents the addition of values
  • X represents each value in the data set
  • µ represents the mean of the data set
  • N represents the number of data values

Grouping of data is very much possible in two ways:

  1. Discrete Frequency Distribution
  2. Continuous Frequency Distribution