Calculatrice d'Écart-type pour 3 Valeurs Gratuite
Calculez rapidement l'écart-type de trois valeurs. Obtenez la variance, la moyenne et l'écart-type en un clic.
Moyenne
20.0000
Formule
Standard Deviation
Formula
Population SD = sqrt(sum of (xᵢ - mean)² / N)
Sample SD = sqrt(sum of (xᵢ - mean)² / (N-1))
Steps
1. Calculate the mean (average) 2. Find each value's deviation from the mean 3. Square each deviation 4. Average the squared deviations (divide by N for population, N-1 for sample) 5. Take the square root
Exemple Résolu
Find the standard deviation of 10, 20, 30.
- 01Mean = (10+20+30)/3 = 20
- 02Deviations: -10, 0, +10
- 03Squared: 100, 0, 100
- 04Variance = (100+0+100)/3 ≈ 66.67
- 05Std Dev = √66.67 ≈ 8.1650
Questions Fréquentes
What is standard deviation?
Standard deviation measures the spread or dispersion of data points from the mean. A low SD means data clusters near the mean; a high SD means data is more spread out.
When do I use population vs sample?
Use population SD (divide by N) when you have data for the entire population. Use sample SD (divide by N-1) when your data is a sample from a larger population.
What is variance?
Variance is the average of squared deviations from the mean. Standard deviation is the square root of variance, bringing the units back to the original scale.
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