First slide

Introduction to statistics

Question

$If \sum_{i = 1}^{60} x_{i}^{2} = 18000, \sum_{i = 1}^{60} x_{i} = 960 then the standard deviation of x_{1}, x_{2}, x_{3}, - - - x_{60} is$

Moderate

Solution

$σ^{2} = \frac{\sum x_{i}^{2}}{n} - {(\frac{\sum x_{i}^{2}}{n})}^{2} = \frac{18000}{60} - {(\frac{960}{60})}^{2} = 300 - 256 = 44$
$∴ S . D . = σ = \sqrt{44} = 6.63$

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