Standard Deviation Formula

หรือเรียกอีกอย่างว่า: Population Standard Deviation, SD Formula

\sigma = \sqrt{\frac{\sum_{i=1}^{N}(x_i - \mu)^2}{N}}

σ = √(Σ(xi - μ)² / N)

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Measures how spread out data points are from the mean. A low SD means data is clustered close to the mean; a high SD means data is spread out.

เครื่องหมาย	ชื่อ	หน่วย	คำอธิบาย
\sigma	Standard Deviation	—	Measure of spread in the data
x_i	Data Point	—	Each individual value in the dataset
\mu	Mean	—	Average of all data points
N	Count	—	Total number of data points

1Mean = 40/8 = 5

2Deviations: -3,-1,-1,-1,0,0,2,4

3Squared: 9,1,1,1,0,0,4,16

4Variance = 32/8 = 4

5SD = √4 = 2

ผลลัพธ์: σ = 2

Population SD divides by N, sample SD divides by N-1

SD is always non-negative

#statistics#data analysis#probability