M. Find the quartile deviati
[1.Q.
uartile deviation and its co-efficient from the following data.
58
1 60 oil ola 64 | 65 | 66 |
Forudents 15 20 32 35 3 22 20 10 18
TOD. = 15. Co-efficientQ,d =0,024
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Step-by-step explanation:
Answer:
Quartiles, Quartile Deviation and Coefficient of Quartile Deviation
The Quartile Deviation is a simple way to estimate the spread of a distribution about a measure of its central tendency (usually the mean). So, it gives you an idea about the range within which the central 50% of your sample data lies. Consequently, based on the quartile deviation, the Coefficient of Quartile Deviation can be defined, which makes it easy to compare the spread of two or more different distributions. Since both of these topics are based on the concept of quartiles, we’ll first understand how to calculate the quartiles of a dataset before working with the direct formulae.
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Measures of Central Tendency
Quartile Deviation and Coefficient of Quartile Deviation
Measure of Dispersion
Quartiles
A median divides a given dataset (which is already sorted) into two equal halves similarly, the quartiles are used to divide a given dataset into four equal halves. Therefore, logically there should be three quartiles for a given distribution, but if you think about it, the second quartile is equal to the median itself! We’ll deal with the other two quartiles in this section.
The first quartile or the lower quartile or the 25th percentile, also denoted by Q1, corresponds to the value that lies halfway between the median and the lowest value in the distribution (when it is already sorted in the ascending order). Hence, it marks the region which encloses 25% of the initial data.
Similarly, the third quartile or the upper quartile or 75th percentile, also denoted by Q3, corresponds to the value that lies halfway between the median and the highest value in the distribution (when it is already sorted in the ascending order). It, therefore, marks the region which encloses the 75% of the initial data or 25% of the end data.
Browse more Topics under Measures Of Central Tendency And Dispersion
Arithmetic Mean
Median and Mode
Partition Values or Fractiles
Harmonic Mean and Geometric Mean
Measure of Dispersion
Range and Mean Deviation
Standard deviation and Coefficient of Variation
Learn more about Standard Deviation, Coefficient of Variation here in detail.
For a better understanding, look at the representation below for a Gaussian Distribution –
quartile deviation
Source – Wikipedia
The Quartile Deviation
Formally, the Quartile Deviation is equal to the half of the Inter-Quartile Range and thus we can write it as –
Qd=Q3–Q12
Therefore, we also call it the Semi Inter-Quartile Range.
The Quartile Deviation doesn’t take into account the extreme points of the distribution. Thus, the dispersion or the spread of only the central 50% data is considered.
If the scale of the data is changed, the Qd also changes in the same ratio.
It is the best measure of dispersion for open-ended systems (which have open-ended extreme ranges).
Also, it is less affected by sampling fluctuations in the dataset as compared to the range (another measure of dispersion).
Since it is solely dependent on the central values in the distribution, if in any experiment, these values are abnormal or inaccurate, the result would be affected drastically.
Learn more about Range and Mean Deviation here in detail.
The Coefficient of Quartile Deviation
Based on the quartiles, a relative measure of dispersion, known as the Coefficient of Quartile Deviation, can be defined for any distribution. It is formally defined as –
Coefficient of Quartile Deviation = Q3–Q1Q3+Q1×100
Since it involves a ratio of two quantities of the same dimensions, it is unit-less. Thus, it can act as a suitable parameter for comparing two or more different datasets which may or may not involve quantities with the same dimensions.
So, now let’s go through the solved examples below to get a better idea of how to apply these concepts to various distributions.
Solved Examples on Quartile Deviation
Question 1: The number of vehicles sold by a major Toyota Showroom in a day was recorded for 10 working days. The data is given as –
Day Frequency
1 20
2 15
3 18
4 5
5 10
6 17
7 21
8 19
9 25
10 28
Find the Quartile Deviation and its coefficient for the given discrete distribution case.
Solution: We first need to sort the frequency data given to us before proceeding with the quartiles calculation –
Sorted Data – 5, 10, 15, 17, 18, 19, 20, 21, 25, 28
n(number of data points) = 10
Now, to find the quartiles, we use the logic that the first quartile lies halfway between the lowest value and the median; and the third quartile lies halfway between the median and the largest value.