Examples
Examples
Try the starting example
- Group A mean
- 10
- Group A standard deviation
- 2
- Group A size
- 20
- Group B mean
- 8
- Group B standard deviation
- 3
- Group B size
- 20
- Welch t
- 2.480695
- Degrees of freedom
- 33.103093
- Two-sided p-value
- 0.018368
Try another scenario
- Group A mean
- 11
- Group A standard deviation
- 2
- Group A size
- 20
- Group B mean
- 8
- Group B standard deviation
- 3
- Group B size
- 20
- Welch t
- 3.721042
- Degrees of freedom
- 33.103093
- Two-sided p-value
- 0.000735
Calculation method
Calculation method
Welch t
Difference in sample means divided by sqrt(sA²/nA+sB²/nB).
Degrees of freedom
Welch–Satterthwaite degrees of freedom = (vA+vB)² / (vA²/(nA−1)+vB²/(nB−1)), where v=s²/n.
Two-sided p-value
Two-sided Student t tail probability I[df/(df+t²)](df/2,1/2).
Symbols and units
- a
- Group A mean
- b
- Group A standard deviation
- c
- Group A size
- d
- Group B mean
- e
- Group B standard deviation
- f
- Group B size
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- Reports Welch t, degrees of freedom and a two-sided p-value; no automatic significance decision. Independent samples are assumed. Assumes independent samples and approximately normal sampling distributions for the group means.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
Background reading; this does not imply endorsement or independent review of SumFizz.