Statistics - Geometric Mean of Discrete Series



When data is given alongwith their frequencies. Following is an example of discrete series:

Items 5 10 20 30 40 50 60 70
Frequency 2 5 1 3 12 0 5 7

In case of discrete series, Geometric Mean is computed using following formula.

Formula

$G.M. = Antilog\ \frac{\sum f \times \log x}{N} \\[7pt] \, = Antilog\ \frac{f_{1} \log x_{1} + f_{2} \log x_{2} + .... + f_{n} \log x_{n}}{N}$

Where −

  • ${G.M.}$ = Geometric Mean

  • ${x_1,x_2,x_3,...,x_n}$ = Different values of variable x.

  • ${f_1,f_2,f_3,...,f_n}$ = Corresponding frequencies of variable x.

  • ${N = \sum f}$

Example

Problem Statement:

Calculate Geometric Mean for the following discrete data:

Items 14 36 45 70 105
Frequency 2 5 1 3 12

Solution:

Based on the given data, we have:

${x}$ ${f}$ ${logx}$ ${flogx}$
14 1 1.1461 1.1461
36 2 1.5563 3.1126
45 1 1.6532 1.6532
70 2 1.8450 3.6900
105 1 2.0211 2.0211
Total     11.623

Based on the above mentioned formula, Geometric Mean $G.M.$ will be:

$G.M. = Antilog\ \frac{\sum f \times \log x}{N} \\[7pt] \, = Antilog\ of\ \frac{11.623}{5} \\[7pt] \, = Antilog\ of\ 2.3246 \\[7pt] \, = 211.15$

The Geometric Mean of the given numbers is 211.15.

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