4- Mean, Variance & Standard Deviation

Ankit Gupta
Sep 9, 2018 · 2 min read

Understanding the relationship among Mean, Variance and Standard Deviation.

Let us assume the height of 5 pets is 6, 4.7, 1.7, 4.3, 3 (in ft)respectively.

Height in Y-axis

Mean = (6+4.7+1.7+4.3+3)/5 = 3.94 ft

So the mean height is 3.94 ft as highlighted below with the yellow line

Mean Line in yellow

Now we calculate each pets’ difference from the Mean. To calculate the Variance, take each difference, square it, and then average the result:

Variance= (2.06²+0.76²+ (-2.24)²+0.36²+0.94²)/5 =2.1704

Variance

Standard Deviation = square-root of Variance = √2.1704 =1.47 ft

Standard Deviation of 1.47 ft

Heights are within one Standard Deviation (1.47 ft) of the Mean. So, using the Standard Deviation we have a “standard” way of knowing what is normal, and what is extra large or extra small.

Credits :- Mathsisfun.com

Ankit Gupta
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