Example: Cell A seal-strength variance
45 independent pouch-strength readings from Cell A; the reference CSV also contains Cell B readings.
Download the study reference (CSV)This is the same example used in Help. The CSV is a reference for the supplied study. Enter the checked summaries manually on Inputs; importing the CSV does not populate this calculator. Use Open example in a practice copy in Help to prefill the inputs.
1. Create the workspace
In the sidebar, open Basic Statistics and choose Confidence Intervals. Create an analysis, name it, select New blank worksheet, then choose Create analysis.
2. Choose the interval
On Inputs, choose Variance (χ²) for Parameter. Enter 0.95 in Confidence level (0–1) for a 95% interval.
3. Enter the summaries
Under Summarized data, enter the following values. Keep the full precision shown for standard deviations. No worksheet columns are assigned.
Enter 45 in Sample size (n).
Enter 1.053112894079627 in Sample standard deviation (s).
4. Run analysis
Choose Run analysis, then open Results.
5. Interpret results
Identify what the interval estimates
45 independent pouch-strength readings from Cell A; the reference CSV also contains Cell B readings. The selected parameter is variance (χ²).
Read the estimate and bounds
The variance estimate is 1.1091 N², with a 95% interval of 0.7601–1.7697 N². Variance is the standard deviation squared.
Keep the interpretation clear
The chi-square interval assumes a normal population and independent observations. It estimates spread, not the population mean or acceptable individual strengths.
Use the uncertainty in the decision
Use variance when a calculation requires squared spread. For a discussion in newtons, use the corresponding standard-deviation interval.
More details: read each result section
Complete result tables use six significant digits, as in Help.
Confidence interval
Parameter names the population quantity. Confidence level 0.95 means this interval method covers the fixed population parameter in 95% of repeated comparable samples under its assumptions. Estimate is the sample-based value; Lower bound and Upper bound mark its uncertainty. Method records the calculation. The chi-square interval assumes a normal population and independent observations. It estimates spread, not the population mean or acceptable individual strengths.
| Statistic | Value |
|---|---|
| Parameter | Variance (χ²) |
| Confidence level | 0.95 |
| Estimate | 1.10905 |
| Lower bound | 0.760077 |
| Upper bound | 1.76968 |
| Method | chi-square |
6. Create a report
Keep the complete Confidence interval table, selected parameter, confidence level, method and entered summaries. The chi-square interval assumes a normal population and independent observations. It estimates spread, not the population mean or acceptable individual strengths.
Choose Add to report from the completed run. Open Choose individual items and advanced options to select tables and charts, then choose Add to draft. Hidden items stay in the saved analysis.
Name the report and add the purpose of the study and your interpretation. Choose Save, review Preview, then use Export → Download HTML. The example below contains the full selected content, including results beyond one screen.