Answer on Question #70890 – Math – Statistics and Probability
Question
What characteristics are important to process when considering a random sample?
Solution
The median is the so-called mean value of an ordered series of values of a random variable:
M e = { x k + x k + 1 2 , n = 2 k , x k + 1 , n = 2 k + 1 , M_e = \begin{cases} \dfrac{x_k + x_{k+1}}{2}, & n = 2k, \\ x_{k+1}, & n = 2k + 1, \end{cases} M e = ⎩ ⎨ ⎧ 2 x k + x k + 1 , x k + 1 , n = 2 k , n = 2 k + 1 ,
where n n n is the size of the sample.
Mode is a value that has a higher frequency than others.
The sampling range is the difference between the largest and smallest values of the random sample:
R = x max − x min R = x_{\max} - x_{\min} R = x m a x − x m i n
Average sample
X ‾ = 1 n ∑ i = 1 n x i \overline{X} = \frac{1}{n} \sum_{i=1}^{n} x_i X = n 1 i = 1 ∑ n x i
Sample variance
σ 2 = 1 n ∑ i = 1 n ( x i − X ‾ ) 2 \sigma^2 = \frac{1}{n} \sum_{i=1}^{n} \left(x_i - \overline{X}\right)^2 σ 2 = n 1 i = 1 ∑ n ( x i − X ) 2
Unbiased sample variance
s 2 = n n − 1 σ 2 = 1 n − 1 ∑ i = 1 n ( x i − X ‾ ) 2 s^2 = \frac{n}{n-1} \sigma^2 = \frac{1}{n-1} \sum_{i=1}^{n} \left(x_i - \overline{X}\right)^2 s 2 = n − 1 n σ 2 = n − 1 1 i = 1 ∑ n ( x i − X ) 2
The mean square deviation
σ = σ 2 = 1 n − 1 ∑ i = 1 n ( x i − X ‾ ) 2 \sigma = \sqrt{\sigma^2} = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} \left(x_i - \overline{X}\right)^2} σ = σ 2 = n − 1 1 i = 1 ∑ n ( x i − X ) 2
The coefficient of variation
V = σ X ‾ ⋅ 100 % = 1 n − 1 ∑ i = 1 n ( x i − X ‾ ) 2 1 n ∑ i = 1 n x i ⋅ 100 % V = \frac{\sigma}{\overline{X}} \cdot 100\% = \frac{\sqrt{\frac{1}{n-1} \sum_{i=1}^{n} \left(x_i - \overline{X}\right)^2}}{\frac{1}{n} \sum_{i=1}^{n} x_i} \cdot 100\% V = X σ ⋅ 100% = n 1 ∑ i = 1 n x i n − 1 1 ∑ i = 1 n ( x i − X ) 2 ⋅ 100%
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