The confidence interval formula in statistics is used to describe the amount of uncertainty associated with a sample estimate of a population parameter. It describes the uncertainty associated with a sampling method.
To recall, the confidence interval is a range within which most plausible values would occur. To calculate the confidence interval, one needs to set the confidence level as 90%, 95%, or 99%, etc. A 90% confidence level means that we would expect 90% of the interval estimates to include the population parameter; 95% of the intervals would include the parameter and so on.
Formula for Confidence Interval
The formula for the confidence interval is given below:
|Confidence Interval Formulas|
|If n ≥ 30||Confidence Interval = x̄ ± zα/2(σ/√n)|
|If n<30||Confidence Interval = x̄ ± tα/2(S/√n)|
- n = Number of terms
- x̄ = Sample Mean
- σ = Standard Deviation
- zα/2 = Value corresponding to α2 in z table
- tα/2 = Value corresponding to α2 in t table
- α = (1 – Confidence Level /100)
Also Try: Confidence Interval Calculator