How it works
Two sample variances are weighted by their n−1 degrees of freedom; group mean differences are not added. This form solves for first group sample deviation; enter the known quantities in Pooled variance, First group size, Second group size, Second group sample deviation.
Inputs and units
| Input | Example value | What to enter |
|---|---|---|
| Pooled variance | 10 | Formula symbol: variance. Enter a numeric value. Must be greater than zero. |
| First group size | 10 | Formula symbol: n1. Enter a numeric value. Use a whole number. Must be greater than zero. |
| Second group size | 10 | Formula symbol: n2. Enter a numeric value. Use a whole number. Must be greater than zero. |
| Second group sample deviation | 4 | Formula symbol: s2. Enter a numeric value. Use a non-negative value. |
Worked example
Show example inputs and results
This example is generated by the same calculation engine using the starting values in the form. Your own inputs produce your own result.
- Pooled variance
- 10
- First group size
- 10
- Second group size
- 10
- Second group sample deviation
- 4
Complete example results
- First group sample deviation
- 2
Reading the result
The result solves for first group sample deviation from the entered quantities. Check the result unit and the formula conditions before using it.
Questions and answers
Can I use the example values for my own calculation?
The example values illustrate the calculation. Replace every input with your own information, especially dates, rates and the selected operation.
When can I use the first group sample deviation result?
This uses independent groups and an equal-population-variance approach. Raw-data merging can produce a different variance. Deviations share one unit; variance is squared.
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method sources: itl.nist.gov