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Options¶
Worked examples
The How-To pages build this chart step by step from sample data, one walkthrough per data layout the tool accepts. Start there if you would rather see a finished result than read the settings.
The Confidence Interval dialog has one configurable setting on the CI Settings tab.
Confidence Level¶
Enter a value between 0 and 1 to set the confidence level. Default is 0.95 (95% confidence interval).
Common values:
| Level | Meaning |
|---|---|
| 0.90 | 90% confidence: narrower interval, less certainty |
| 0.95 | 95% confidence: standard default, balances width and certainty |
| 0.99 | 99% confidence: wider interval, more certainty |
Higher confidence levels produce wider intervals because a larger range is needed to be more confident that the true parameter falls within the bounds. Lower confidence levels produce narrower intervals but with less certainty.
A negative count under CI for Poisson Rate¶
A Poisson rate counts occurrences, so it has no meaning for a negative value. The dialog no longer offers a column that holds one: CI for Poisson Rate takes a Count column, and a column of whole numbers becomes Integer as soon as one of its values is negative. See Preparing Your Data for the full table.
If a negative value still reaches the calculation, for example from an analysis restored from a saved worksheet, the run now stops and reports that there is not enough usable data. Earlier versions could not recover from it: the calculation failed, the dialog reopened, and it failed again the same way, which left Excel repeating the cycle.