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Confidence Interval¶
Calculate confidence intervals for the mean, standard deviation, binomial proportion, or Poisson rate.
What is a Confidence Interval?¶
A confidence interval provides a range within which a population parameter is likely to fall at a specified confidence level (e.g., 95%). Quantum XL produces a whisker chart showing the lower and upper bounds with a center marker, plus a statistics table with the interval details.
Four CI Types¶
Four confidence interval types are available, each selected from a separate item in the Excel ribbon dropdown:
| Type | Distribution | When to Use |
|---|---|---|
| CI for the Mean | t-distribution | Estimate where the true population mean lies based on sample data |
| CI for Standard Deviation | Chi-squared | Estimate the range of the true population standard deviation |
| CI for Binomial Proportion | Beta (Clopper-Pearson exact) | Estimate the true proportion when data has exactly 2 outcomes (e.g., Pass/Fail) |
| CI for Poisson Rate | Chi-squared (exact) | Estimate the true rate of occurrence for count data (e.g., defects per day) |
Example Output¶
A typical output shows a whisker chart with vertical lines extending from the lower bound to the upper bound, a diamond marker at the center value, and a statistics table alongside with sample size, point estimate, and interval bounds.
What the sheet records about your settings¶
The Confidence Interval sheet has no Settings block. It states the one setting that matters in the results heading instead, which reads 95% Confidence Interval Results with your own level in place of the 95. The level is printed as you set it, so a level of 97.5 per cent reads 97.5% Confidence Interval Results rather than being rounded.
Learn More¶
- How-To: Step-by-step tutorials for each CI type
- Preparing Your Data: Data types, column requirements, and the behavior matrix
- Options: Confidence level setting