1.

Find the SD of the following set of observations 45, 36, 40, 37, 39, 42, 45, 35, 40, 39.

Answer»

\(\bar x = \frac{\sum x_i}{n}\) 

\(=\frac{45+36+40+37+39+42+45+35+40+35}{10}\) 

\(=\frac{398}{10}=39.8\)

Now,

xixi - \(\bar{\text x}\)(xi - \(\bar{\text x}\))2
455.227.04
363.814.44
400.20.04
372.87.84
390.80.64
422.24.84
455.227.04
354.823.04
400.20.04
390.80.64
\(\sum(x_i-\bar x)^2=105.6\)

\(\therefore \) Standard deviation is \(\sigma = \sqrt{\frac{\sum(x_i-\bar x)^2}{n-1}}\) 

 = \(\sqrt{\frac{105.6}9}\) = \(\sqrt{11.73}\) = 3.425

\(\therefore \) Standard deviation of given observation is 3.425



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