Calculateur d'Intervalle de Confiance Gratuit

Calculez les intervalles de confiance pour les moyennes de population.

Lower Bound

46.7333

Margin of Error3.2667
Erreur type1.6667

Lower Bound vs Sample Mean

Voir la formule →

Formule

## How to Calculate a Confidence Interval ### Formula **CI = x_bar +/- z * (sigma / sqrt(n))** The confidence interval gives a range of plausible values for the population mean. The standard error (sigma/sqrt(n)) measures how much the sample mean varies across samples. The z-value determines the confidence level: 1.645 for 90%, 1.96 for 95%, 2.576 for 99%.

Exemple Résolu

Sample mean = 50, SD = 10, n = 36. Build a 95% confidence interval.

  1. 01Standard Error = 10 / sqrt(36) = 10 / 6 = 1.6667
  2. 02Margin of Error = 1.96 * 1.6667 = 3.2667
  3. 03Lower bound = 50 - 3.2667 = 46.7333
  4. 04Upper bound = 50 + 3.2667 = 53.2667
  5. 0595% CI: (46.7333, 53.2667)