Does this use a t-score for small samples?
This calculator focuses on z-intervals. For very small samples where σ is unknown, consider substituting a t critical value manually.
Step-by-step walkthrough
Confidence Interval Calculator Guide
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Before you start
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
- confidence interval
- z interval
- margin of error
Detailed procedure
Step 1
Provide your sample mean and standard deviation.
Step 2
Enter the sample size that produced those statistics.
Step 3
Pick a confidence level to update the Z-score and interval bounds.
Teaching & troubleshooting tips
Can I interpret the interval as probability?
Not directly. A 95% interval means that if you repeatedly sampled and built intervals the same way, about 95% would capture the true mean.