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Calculation of Median

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Calculation of Median

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This power point explains the methods of median calculation in individual series, discrete series and continuous series.

This power point explains the methods of median calculation in individual series, discrete series and continuous series.

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Calculation of Median

  1. 1. Calculation of Median SUBMITTED BY DR. SUNITA OJHA ASSISTANT PROFESSOR SURESH GYAN VIHAR UNIVERSITY
  2. 2. Median • The median is usually defined as that value which divides a distribution so that equal number of items occur on either side of it. • In other words 50 percent of the observations will be smaller than the median and 50 percent of the observations will be greater than the median. 1. Calculation of median in a series of individual observations: • Arrange the data in the ascending or descending order • Median is located by finding the size of the (n+1/2)th item. 𝑴 = 𝒏 + 𝟏 𝟐 𝒕𝒉 𝒊𝒕𝒆𝒎 M= Median n= number of observations Example 1. Find out the median from the data recorded on the number of clusters per plant in a pulse crop: 10,18, 17, 19, 10, 15, 11, 17, 12
  3. 3. S. No. Data arranged in ascending order 1 10 2 10 3 11 4 12 5 15 6 17 7 17 8 18 9 19 Median = Size of (n+1)/2 th item = (9+1)2 th item =5th item Median = 15 2. Calculation of median in a discrete series • Data should be arranged in ascending or descending order of magnitude • Find out the cumulative frequencies • Median= size of the (n+1)/2 th item • Find out the (n+1)/2 th item. It can be found by first locating the cumulative frequency which is equal to (n+1)/2 or the next higher to this and then determine the value corresponding to it. This will be the value of median.
  4. 4. Example 1. Find out the median of the following data No. of angular seeded plants 12 8 17 10 11 16 18 14 6 7 No. of plants 39 33 42 40 47 42 60 50 22 25 No. of angular seeded plants No. of plants Cumulative Frequency 6 22 22 7 25 47 8 33 80 10 40 120 11 47 167 12 39 206 14 50 256 16 42 298 17 42 340 18 60 400 Median = (400+1)/2 th item =200.5th item Median=12
  5. 5. 3. Calculation of median in a continuous series • While computing the value of the median in a continuous series, first determine the particular class in which the value of the median lies. • Use n/2 as the rankof the median and not (n+1)/2 𝑴𝒆𝒅𝒊𝒂𝒏 = 𝑳 + 𝒏 𝟐 − 𝒄𝒇 𝒇 × 𝒊 L= lower limit of the median class cf= cumulative frequency of the class preceding the median class f=frequency of the median class i= class interval
  6. 6. No. of grains per earhead classes Frequency Cumulative frequency 5-10 2 2 10-15 27 29 15-20 52 81 20-25 118 199 25-30 57 256 30-35 27 283 35-40 13 296 40-45 4 300 Example 1. Calculate the value of the median from the data recorded on the number of grains per earhead on 300 wheat earhead. Solution: Median= Size of (n/2)th item= 300/2= 150 Median lies in the class=20-25 L=20; n/2= 150; cf=81; i=5; f=118 Median=20+(69/118)*5 =20+2.92 =22.92
  7. 7. 4. Calculation of median in unequal class- intervals • In unequal class-interval frequencies need not be adjusted to make the class intervals equal and the formula can be used here. 𝑴𝒆𝒅𝒊𝒂𝒏 = 𝑳 + 𝒏 𝟐 − 𝒄𝒇 𝒇 × 𝒊 n/2=70/2= 35 Median= 30+ ((35-21)/10)*10 = 30+(140/10)*10 =30+14 =44 Classes Frequency Cumulative Frequency 0-10 5 5 10-30 16 21 30-60 30 51 60-80 12 63 80-90 6 69 90-100 1 70 Classes Frequency Cumulative Frequency 0-10 5 5 10-20 8 13 20-30 8 21 30-40 10 31 40-50 10 41 50-60 10 51 60-70 6 57 70-80 6 63 80-90 6 69 90-100 1 70
  8. 8. 5. Calculation of median in open-end classes • Since the median is not affected by the values of extreme ends we are not concerned with the extreme values for the calculation of median in open-end classes. Size of item classes Frequency Cumulative Frequency Less than 10 4 4 10-20 8 12 20-30 14 26 30-40 6 32 40 and above 4 36 Example 1. Calculate the median in open –end series. Solution: 𝑴𝒆𝒅𝒊𝒂𝒏 = 𝑳 + 𝒏 𝟐 − 𝒄𝒇 𝒇 × 𝒊 n/2= 36/2= 18th item Median lies in the class 20-30 Median= 20+((18-12)/14)*10 =24.29
  9. 9. 6. Graphic Location of Median: • Draw two ogives one by less than method and the other by more than method. • From the point where the two curves intersect draw a perpendicular line to the X- axis. The point on the X-axis will give the median value.

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