A sample of 100 monthly profits gave out the following data: $ \sum_{i=1}^{100} x_i = 3,453 \quad \text{and} \quad \sum_{i=1}^{100} x_i^2 = 800,536 $ What is the sample mean and standard deviation of the monthly profits? | Financial Risk Manager Part 1 Quiz

A sample of 100 monthly profits gave out the following data:

\sum_{i=1}^{100} x_i = 3,453 \quad \text{and} \quad \sum_{i=1}^{100} x_i^2 = 800,536

What is the sample mean and standard deviation of the monthly profits?

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Explanation:

Calculation Explanation

The sample mean is calculated as:

\hat{\mu} = \bar{X} = \frac{1}{n} \sum_{i=1}^{n} X_i

\Rightarrow \bar{X} = \frac{1}{100} \times 3,453 = 34.53

The sample variance is calculated using:

s^2 = \frac{1}{n-1} \left\{ \sum_{i=1}^{n} X_i^2 - n \hat{\mu}^2 \right\}

s^2 = \frac{1}{99} (800,536 - 100 \times 34.53^2)

34.53^2 = 1192.3209

100 \times 1192.3209 = 119,232.09

800,536 - 119,232.09 = 681,303.91

s^2 = \frac{681,303.91}{99} = 6881.857677

s = \sqrt{6881.857677} = 82.96

Therefore, the correct values are:

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