Determine the confidence level you want, such as 90%, 95%, or 99%
Calculate alpha: alpha = 1 – confidence level
For a two-tailed interval, divide alpha by 2
Find the critical value from the appropriate distribution
Use z for large samples or known population standard deviation
Use t for small samples or unknown population standard deviation
Compute the margin of error: critical value × standard error
Calculate the confidence interval: estimate ± margin of error
Express the confidence level as the percentage associated with the interval
Interpret the result as the proportion of intervals that would contain the true parameter in repeated sampling