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- 1. Calculation of Arithmetic Mean SUBMITTED BY DR. SUNITA OJHA ASSISTANT PROFESSOR SURESH GYAN VIHAR UNIVERSITY
- 2. Arithmetic Mean • It represents the entire data by one value which is obtained by adding together all the values and dividing this total value by the number of observations 1. Calculation of Arithmetic Mean of an individual Series • This can be calculated by direct method or short-cut method. The result will be same for both methods. Direct Method: 𝑿̄̅ = ∑𝑿̄̅ 𝒏 X̄= arithmetic mean ∑X= sum of all values of the variable x i.e. X1, X2, X3, …… Xn n= No. of observations Example 1. Calculate the arithmetic mean of the following set of observations: 7, 6, 8, 10, 13, 14 X̄= ∑x/n =58/6= 9.67
- 3. Short Cut Method: X = 𝑨 + ∑𝒅 𝒏 X̄= arithmetic mean A= Assumed mean d= deviation of items from the assumed mean (x-A) ∑d= sum of all deviations n= No. of observations Example 2: Calculate the arithmetic mean of the data given: X̄= A+ ∑d/n =24+13/10 =25.3 No. of spikelets per spike Deviations from the assumed mean Assumed mean=24 18 -6 19 -5 20 -4 21 -3 22 -2 28 4 29 5 30 6 31 7 35 11 n=10 ∑d=-20+33=13
- 4. 2. Calculation of Arithmetic Mean in Discrete Series The values of the variables are multiplied by their respective frequencies. The number of observations is the total number of frequencies. Direct Method: 𝑿̄̅ = ∑𝒇𝑿̄̅ 𝒇 X̄= arithmetic mean ∑fX= sum of values of the variables and their corresponding frequencies ∑f= sum of frequencies. Example 1. 𝑿̄=(∑𝒇𝑿)/𝒇 =391/150 =2.61 Short cut method: 𝑿̄̅ = 𝑨 + ∑𝒇𝒅 ∑𝒇 X̄= arithmetic mean A= Assumed mean No. of chlorophyll deficient plants No. of plants fx 0 34 0 1 14 14 2 20 40 3 24 72 4 25 100 5 33 165 ∑f=150 ∑fX=391
- 5. d= deviation of items from the assumed mean (x-A) ∑fd= sum of the deviations from the assumed mean and the respective frequencies ∑f= sum of the frequencies 3. Calculation of Arithmetic Mean in Continuous Series In a continuous series, the arithmetic mean may be calculated after taking into consideration the mid point of various classes. The method will be the same for both inclusive class-intervals as well as for exclusive class-intervals. Direct Method: 𝑋 = ∑𝑓𝑚 ∑𝑓 X̄= arithmetic mean ∑fm= sum of values of midpoints multiplied by the respective frequencies of each class ∑f= sum of frequencies m= midpoint of various classes. Mid-Point (m)= (Lower limit + Upper limit)/ 2
- 6. Plant Height Classes No. of varieties (f) Mid-points (m) fm 0-10 5 5 25 10-20 10 15 150 20-30 25 25 625 30-40 30 35 1050 40-50 20 45 900 50-60 10 55 550 ∑f= 100 ∑fm=3300 Example 1. Compute the arithmetic mean of the following data 𝑋 = ∑𝑓𝑚 ∑𝑓 X̄= 3300/100 =33
- 7. Short cut method: 𝑋 = 𝐴 + ∑𝑓𝑑 ∑𝑓 X̄= arithmetic mean A= Assumed mean d= Deviation of midpoints from the assumed mean (m-A) ∑f= sum of frequencies f= frequency of each class 4. Calculation of arithmetic mean in series having open-end classes No. of pods No. of plants Below 10 4 10-20 6 20-30 20 30-40 12 40-50 10 50-60 5 Above 60 4 No. of pods No. of plants 0-10 4 10-20 6 20-30 20 30-40 12 40-50 10 50-60 5 60-70 4 ‗ > In this data the class interval is uniform therefore the lower limit if the first class would be zero and the last limit would be 70
- 8. References Khan, I. A., & Khanum, A. (1994). Fundamentals of biostatistics. Ukaaz. Sharma, A. K. (2005). Text book of biostatistics I. Discovery Publishing House. Daniel, W. W., & Cross, C. L. (2018). Biostatistics: a foundation for analysis in the health sciences. Wiley.