Measures of Central Tendency and DispersionPYQ May 25Question 4074 of 473
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Which one of the following is the absolute measure of dispersion for open ended distributions?

Options

ARange
BStandard deviation
CMean deviation
DQuartile deviation
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Correct Answer

Option dQuartile deviation

All Options:

  • ARange
  • BStandard deviation
  • CMean deviation
  • DQuartile deviation

Detailed Solution & Explanation

An open-ended distribution is one where the lower limit of the first class interval and/or the upper limit of the last class interval are not specified.
Let us evaluate the suitability of each measure of dispersion for open-ended distributions:
1. **Range**: Requires the absolute minimum and maximum values of the entire distribution, which are unknown in open-ended classes.
2. **Mean Deviation** and **Standard Deviation**: Require calculation of the class midpoints (mid-values) for all classes. Since the boundary values of open-ended classes are missing, midpoints cannot be computed.
3. **Quartile Deviation**: Depends only on the quartiles Q1\displaystyle Q_1 and Q3\displaystyle Q_3, which are partition values calculated from the cumulative frequencies. Because Q1\displaystyle Q_1 and Q3\displaystyle Q_3 fall within the middle 50% of the distribution, their calculations are completely unaffected by open-ended extremities at either end.
Thus, Quartile Deviation is the only absolute measure of dispersion suitable for open-ended distributions.

Hence, **Option D** is the correct answer.

About This Chapter: Measures of Central Tendency and Dispersion

Paper

Paper 3: Quantitative Aptitude

Weightage

12-15 Marks

Key Topics

Mean, Median, Mode, Range, Mean Deviation, Standard Deviation

The core foundation of Statistics. This chapter covers Mean (Arithmetic, Geometric, Harmonic), Median, Mode, and their properties. It also explores measures of spread like Range, Mean Deviation, Standard Deviation, and Quartile Deviation.

View Official ICAI Syllabus

Exam Strategy Tip

Do not just memorize formulas; ICAI loves asking about the mathematical properties (e.g., 'sum of deviations from the AM is always zero'). You can usually eliminate 2 options just by knowing the properties.

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